Need Help Bad! Mechanic cant find problem!
 

Hey guys, my dad took my car to the mechanic yesterday and they looked at the car for 7 hours and couldnt find what was wrong. If you didnt see my post from last week, the car started acting up a little at idle at first. This was around a month ago. After only missing and surging a little bit at an idle, the car began to stall out at idle, and also cut out for a spilt second and stutter while cruising at low rpms. Now the damn thing runs ok while cold, but once it heats up it hardly runs. It surges like crazy at an idle, constantly misses and hesitates at cruising speed, and sometimes kicks in and goes and sometimes when i punch it it hesitates, revs to like 3 grand and even backfires sometimes. WTF! This is really pissing me off considering im in school 200 miles away and rush home every weekend to figure this crap out. So far i have checked the egr, checked for any vacuum leaks, and someone even told me it might be the tps, so i even went out and replaced and volt-tested it. I even went further and replaced the cap and rotor and all the plug wires. No difference after any of this. Another thing that is interesting is when the car first acted up at all, I was driving in the rain. I find it hard to believe this is just a coincidence, but it may be. Have you guys ever heard of anthing like this before? The mechanic also said that it must be a problem with the computer. He said the options I have are to either get a new comp. and harness or switch to carb. What's up with that? Im really pissed. If you guys can help me out at all, either by giving me some input, or slipping some dynamite in the car late at night, I would really appreciate it. Thanks Alot, John

We just had a simalar problem with our 88GT,, when it warmed up sometimes it really ran like crap, wouldn't idle, stall out sometimes backfire, missing.. This drove us crazy. Took it to a Mustang shop here and it took them sometime to figure it out. What they found was the distributor module (think that's what it's called) was shorting out when the engine warmed up causing all kinds of these problems. Once the module was replaced - haven't had a problem since.

Are you referring to the tfi module that mounts to the side of the distributor? I had onre laying around my house amd swapped that one in, but the car still did the same crap. I dont know if the one i a swapped in was bad also or not, but thatnks for the help anyway, maybe ill try to get one off a friends car and see if that on works. Thanks again - John

Yo,

If you all are talking about TFI modules (which pulg into the distributor) then you are all having the same problem. The reason for this is becuase Ford has RECALLED ALL OUR CARS!! The other day I received the form in the mail. Basically, what happened is that the TFI modules failed under heat and cause some peoples cars to straight up die while driving and in traffic. Lot's of injuries and I belive even deaths. The claim is being made againast Ford by MILLIONS of people. This wasn't just a Stang problem...it ranged from Aerostars & Taurses to Lynx's.

You CAN get reimbursed for this and I suggest calling your nearest Ford dealer (know...this isn't a commercial) and tell them to set up an appointment to get this fixed. The document I received had to come from the Ford dealer (when I "got" my sticker last summer) knowing my info then because I bought my car without an engine or tranny. Either way, call them and good luck. I'll try to find the remainder of the claim form but I think I threw it away.

Good luck!

A bad TFI module usually results in a no start condition when warm. It sounds alot like a bad MAP sensor, but you're engine is MAF. Have you tried pulling codes? That would help alot.

Take care,
-Chris

TFI module it is,,, when the car got warm and was missin and spittin.. Finally wouldn't start.. Let the car sit for a while and it would start and run just fine. I would suggest getting a new one they're not expensive.

i got my recall form for the tfi the other day i have not got the chane to take it in yet to have it looked at to see if it has been replaced yet or not (2nd owner) i have not had any probs myself but if i was you i wsould take you car to a ford dealer and have your tfi module replaced it may solve your prob and ford will pay for in my opinion its worth a shotb

tfi modules have been known to do that and since its a recall on all fords it cant hurt to take it in for a check up at your local dealer. it is free. unless they try to get over on you. however, dont forget about the simple mechanical stuff. the fuel pump can also do that. have you checked that? have you changed the fuel filter? always start with basics. dont assume that just because you have fuel pressure its ok. you also need volume.

I'd have to agree with juiceman. The fuel pump seems a little suspect to me as well. As far as the MAP/BAP sensor, they act when the car is cold as well. If it was faulty, it would probably show up right away. EGR is the same way. Cold/hot, doesn't matter. The O2 sensors may be causing some problems, but it would have to be really bad to have the car stall out.

Something else to note, the MAP/BAP, O2, EGR, all those will pretty much be negated when the car is floored. Almost all the emissions equipment goes off line. The fuel pump obviously doesn't. ;)

I would bet on fuel pump, or an ignition problem.

Just a thought, but have you checked your timing? When I put new heads, cam intake etc. on my car a month ago and first started it up i had the same problem and it turned out the timing was way retarded. Like I said it's just a thought, hadn't noticed anyone mention it and it's easy to check.

Hey thanks for the replies guys. I have changed the fuel filter and it didnt fix anything. I am going back home tomorrow and ill definitely check the fuel pump. Also I have all my smog crap removed and my o2 sensors are not even hooked up, the harness is not long enough to reach where the senso mounts on my longtubes. It may be possible my timing is off, I havent messed with it ever. But would the car run fine sometimes and not others if the timing is off? Thanks for all the help - John

Oh I forgot to mention one thing regarding the o2 sensors. When i put the headers on and noticed that i couldnt connect them, the guy who helped me install them said it would be ok just to secure the unused harnesses under the car. Is it possible that water may have gotten to them and caused something to go screwy in the comp.? Just a thought. -John

I completely disagree with the idea of leaving your O2 sensors disconnected, but to answer your question, yes, if the wires became shorted, there would be a problem. It works something like this; The wire that sends a signal to the ECM could become shorted to ground, either directly or via the ground wire in the harness. This would send a signal to the ECM of greater than 1.0 vdc, which would cause the ECM to go into self test mode. The MIL would flash, and the engine would either stall, or drive poorly. If you insist on leaving the O2 sensors disconnected, you need to make sure that the wiring harness that went to them is wrapped and protected from anything that could cause a short to ground.

Take care,
-Chris

I'd hook up the O2 sensors first off and see if that helps it out, it really should, i don't see anyway your car could idle or run without them connected. It wouldn't affect WOT operation however so there could be another problem as well, fuel pump, tfi, etc.....good luck figuring it out.

RYAN

Man I would suggest take the easy road first - get the TFI module recall done at Ford first... I think you're going to find that's the problem. We did the routine of replacing the fuel filter and other process of eliminations.

I didnt want to leave the o2 sensors disconnected, but the wires dont reach to hook up, the sensors mount on the longtubes further back then they mount on the stock headers. I have had them like that for over 2 months now and all of a sudden it started acting up. Also, I did already replace the tfi with one I had laying around. That one could have been bad too, I dont know. I bought some parts a while ago from a friend and he threw a bunch of other stuf my way, including one of those. It was used, so it could be bad. Thanks - John

just out of curiousity, how many miles on the motor? or better yet, how many miles on the timing chain and gear?? this sounds like a problem i had with my old cougar, result was a warn timing chain and gear.

Maybe this can be helpful...when I was building my car I read an article on a swap in an older mustang to a EFI 302. Obviously they needed to hook up a computer and the article stated that of all the sensors you could ignore, the O2 sensors aren't one of them. I thimk they said you can even skip the PCV but i do remember them saying you have to install the O2 sensors and the MAF. I agree with Chris in that you need to have some O2 sensors if the car is on the street. But the TFI mod is a possibility and it's free so there's no excuse to have it checked. Keep trying. You'll get it.

If a mechanic looked at the car he would have noticed the errors for o2 sensors and the car would not run correct when started that is why they must be pre-heats the car would run like crap at low and cold rpms but run great at high and warm rpms. If I was to guess without even looking at it I would say you have a timed vacuum switch gone bad leaking at warm up and the one that is bad is one that is closed at cold start up. That would lead to the idle circuit and the EGR circuits.

Do you have any cats in your exhaust? The more I read your first post, the more it sounds like a restricted exhaust. Running without the O2 sensors hooked up will keep the ECM in open loop, which means running rich. Running rich will clog up cats, if you have any. Do you have a vacuum gauge you can use?

Why can't you just cut and splice some wire to extend the O2 sensor connections?

As far as TFI, if that doesn't work, I know the PIP inside the dizzy can cut out for split second and the cut right back on. This is hard to catch without a quick multimeter.

Just my $.02
Dave

Hey guys, I dont have any cats or smog stuff on my car. I have mac longtubes running intop a prochamer then to a mac cat-back. I dont have a vaccum guage either. The odometer reads 79,000 but the more i mess with the car, the more i wonder if its really true. The mechanic said he couldnt pull any codes from it because the car was so mixed and matched. I have no idea what the history of the car is, the carfax report doesnt say anything but something is definitely screwy. The car is an 87, but the motor is mass-air. Werent 87-88 models speed density? Anyway, I am going to look at the car tomorrow since I am home now. Hopefully I can get this straightened out. Thanks - John

Oh and hey Hiflow, did your car seem to run ok for the first few minutes then get worse, or was it running crappy all the time?

Oh gees its been almost 4 years since I owned that car....ummm lets see. It started just as back firing once and a while. Then a few months later it sputtered a lot more and started getting rougher. At an idle the car felt like it had a cam in it, and when I went to put it in drive it would die. If I raised the rpms's at idle it would smooth out, but not a hole lot. Hope that helps some.
-Craig

John,
It sounds like you're going through what I went through when I first got my 88. Someone's hands had been all in it that didn't know what they were doing. It had been converted to mass air and when I tried to pull the codes, I had to do some crazy stuff just to get the code reader to pull anything. I had to connect one wire to the positive side of the battery, then another to the EEC ground, or something like that (sorry it's been a while). Then it would pull like 12 codes. I replaced the EEC, and that fixed part of my problems, but not all of them. Anyways the best thing that I can suggest you do is grab a haynes manual for your car and pull the passenger side kick panel off and start referencing wires. Make sure they're where they need to be especially for the MAF. There are 4 wires from the MAF that SOMEBODY obviously put in there, or at least attempted to. Make sure the wiring diagram matches up with your wiring. Then if you still have problems, try and borrow a friend's EEC out of another 89-93, and see if that makes a difference. If you don't already have one, then go get a code scanner from the parts store for about $35.
Dave

im going to give you some advice that im sure pkrud and others will agree with. the first thing you need to do is fix what you know is wrong. you have a computer car and you have computer sensors not even connected. the comp needs to have sensors to properly run the motor. if you didnt hook up your modem would it work? well the car is the same way. next, the mechanic couldnt pull codes? it doesnt matter where the comp came from or when it was put in it still has memory. so if your mechanic knows how to hook up the box then it will give some code, at least an ok code. now im not saying any of those things are your problem and many things as you can see can cause the same reaction on the motor but you need to start at A before you go to B. each part on the motor works together, if you break one thing it will affect the other in some way. one question, didnt your sig say going to carbed? if so why bother fixing the problem, just go carbed now

Ummm... yeah. Your mechanic is a moron. Your car isn't going to run for **** without the O2 sensors hooked up. I suggest you get a longer harness, or an extention harness.

Yeah I was going to go carbed when i first decided to build a motor because my buddy was running a carbed 306 and it was making awesome power, he told me it was cheap so i figured thats what i would do. Since then ive gone off to school and have decided to keep the car efi, since I take the car 180 miles to school. I have added a few mods to the stock motor such as a cold air kit, exhaust and all the small stuff. I have a shortblock for a 331, I just have to wait until summer so i can get a good job and finish it. Anyway I did drive the car earlier and it runs fine at cruising speed now. what the hell! last time i drove it it ran ok for a few mins then got crappy. I just drove the car 25 miles and the damn thing only acted up at idle. This is really ticking me off. I am going to hook up the o2 sensors tomorrow first thing. Does it make sense that the car ran ok for almost 2 months without them being hooked up, but now suddenly went screwy? Thanks for all the suggestions and help because im pretty lost. -John

Almost bet on O2's
 

I would bet that your problem stems from the disconnected O2's. First, did the car run correctly before you put in the long tubes? If so, I am all most certain it is the disconnected O2s. In your first post, you mentioned that the car ran fine cold until it warmed up. Here's how I think why, at around 160F the EEC gives the O2's air/fuel ratio control for the engine. I believe the car ran ok before the rain incendent is because the EEC uses an adaptive fuel mapping logic, it watches for variations in the O2 sensor signal. If the EEC senses that the O2 singal tends to bias toward a lean or rich condtion the EEC will try to compensate for a better 14.0:1 ratio. Which might explain why the car still ran because the computer tried to keep the fuel ratio close until it could no longer compensate or until it recieved a new crazy singal from your water shorted O2 connector plugs. Futhermore, the EEC is constantly monitoring the input/output signals to the computer looking for variations, and when it finds one, it will assign a code to it based on the findings/variations from the norm and store it in memory until you pull them out. And as for your last entry you mentioned the the car is staring to run a little better, that is because the computer is adapting to the new conditions as best it can. My suggestion is to either get new O2's with 16'' leads or buy the extensions for your exsiting O2's but if they are the originals it might be a good idea to replace them. Sorry for such a long post.. but I too have a highly modified stang and have been wrestling with the surging idle FOREVER until I finally sat down and learned how the whole system works. Now she purrs like a kitten. Ok I'm done now.:D

02 sensors?
 

Lemme get this straight since i have an offroad h pipe , i do not have my 02 sensors plugged...Could this be bad?, What kinda problems should i look for if something starts to identify it as o2 sensor wires?

Man I sure hope your right Shogun. What you say really makes sense to me so I hope thats it. Im getting ready to go put the car on a lift now and hook the o2 sensors up. Thanks alot for the help and Ill let you know if it works - John

o2's
 

Well, a hole host of things could happen, such as poor idle quaility, hesititations or backfires at low speed operation, and increased fuel consumtion to name a few.

hey glad I could help I hope it works for ya!

The 02's MUST be hooked up man! those are the sensors that are key to your proper air/fuel ratio! no wonder it won't run right.

WOW:rolleyes: