Fuel Issue

[5150coupe]

This issue just started about two weeks ago and seems to be getting worse. It seems that i am not getting enough fuel at times. I first noticed it on my way to work in the morning. I would drive about three blocks and all of the sudden the car would bog down and start popping when i gave it throttle. After another block it would start running strong without issue. Now it I am having this issue more often, whether the engine is hot or cold. I changed the fuel pump along with the in tank and out of tank filters. I also changed the spark plugs. I thought about the tps, but i'm not sure if this could cause the issue. I did change the tps for another one i had laying around. I do have a manifold leak, so maybe that is slowly getting worse. I'm not sure at this point and would appreciate any suggestions. Thanks.

[USMC302]

Vacuum could certainly be a problem to look into. What is your timing at? Did this problem start after you swapped the TPS? DId you check the voltage on the TPS after putting the new one on? Have you tried pulling any codes? How old are your O2 sensors? Also you didn't mention what year your car is, does it have any other modifications, tell us some about your car to help diagnose or guess (lol) your problem.

[5150coupe]

thanks for the reply, I think i found the issue though. when i installed my trick flow track heat manifold recently i removed the piping going to the heater and the ect along with it. i thought the ect was the other sensor used for the heater guage. i also had a hard time finding any pictures of the ect installed on a 5.0, so it took a while to figure out. the manifold came to me capped, and i don't need the heater, so i left this piece out. the only option that i can see is to add the piping back in or somehow connect the sensor directly to the block. the only thing i can't figure out is how the car ran for a few weeks without issue with the ect removed? somme modifications include a 76mm C&L, bbk 70mm tb, trick flow track heat upper and lower.

[5150coupe]

just installed the ect guage and it still runs the same. I installed the guage directly to the manifold, so i'm not sure if it is getting a correct reading. I left the car in the garage with the positive terminal off to clear the computer in hopes that this might help. also, maybe the computer has to adjust? not sure, but we will find out after a day or two of driving.

[USMC302]

ECT, as in the Engine Coolant Temp sensor? You said you installed the ect guage......? I'm lost. The ECT will not effect the way the car runs. Try taking a look at some of the things I mentioned before and let us know. Again, what year is your car and have you ever changed the 02 sensors? If so how long ago?

[5150coupe]

To answer the previous questions: my timing is at 14, the car did run ok after I initially swapped the tps, and I recently swapped it again as described, didn’t check the voltage since my meter isn’t working right now, haven’t tried pulling codes which is probably the best place to start but the engine was swapped and I’m not sure if the diagnostic will work properly, and the o2 sensors came with the car about six months ago. This is a 1989 lx coupe.

Update with ect: maybe I’m using the wrong terminology, but I believe it is the ect that gives a reading to the computer that in turn tells the injectors to run rich when the motor is cold and lean when the motor is hot, but maybe it is called something else. Anyway, I installed the sensor that was missing directly into the port right above the thermostat in the manifold and the car seems to run a lot better. For the first time in a few weeks the car didn’t seem to run lean in the same places as before. I only had an issue once about halfway to work where I lost a little power and it popped a little, but nothing compared to how it was before. No issues on the return trip home so I am hoping this will fix the issue. The ect is important since it tells the computer when the engine is cold and then warm. The computer compiles information from the ect and other sensors to manage the fuel properly. So if the ect isn’t connected the car can run to lean in a certain period of time and rpm range after starting the car and before it fully warms up. After closer monitering I did realize the issue was happening during warm up and in 2 and 3 gears mostly which is a cruising speed. I’m certainly not an expert though, and am basing this information on other web sites rather than experience, but if the issue I am having does go away then this could prove to be useful information to others.

[USMC302]

Originally Posted by 5150coupe

Update with ect: maybe I’m using the wrong terminology, but I believe it is the ect that gives a reading to the computer that in turn tells the injectors to run rich when the motor is cold and lean when the motor is hot, but maybe it is called something else.

The 02 sensors are going to detect the rich or lean condition and tell the computer to give or take fuel away. The ECU constantly tries to achieve a 14.7 a/f ratio. Might try cleaning the MAF as well, it monitors how much air is coming into the engine ad in return tell the computer how much fuel to add to achieve the desired a/f ratio...The best way to see if your running lean is to install a wideband, from there we can really see what's going on.

Originally Posted by 5150coupe

Anyway, I installed the sensor that was missing directly into the port right above the thermostat in the manifold and the car seems to run a lot better. The ect is important since it tells the computer when the engine is cold and then warm.So if the ect isn’t connected the car can run to lean in a certain period of time and rpm range after starting the car and before it fully warms up.

This really doesn't make sense to me, I'm no expert either but I've run my autometer guage wire off of the ECT for a few years now with NO other wiring going to the ECT and never had any problems. Which means the ECU doesn't even see that I have it plugged in. The sensor your plugging into above the thermostat is going to be for your knowledge only, I don't beleive it sends any signal to the ECU. I believe there is another place or sensor that the ECU gets the temp signal from. I can unplug my Autometer guage from the ECT sensor and my PMS still reads the engine temp from somewhere else...

You said your running a 76mm C&L, are you running stock 19lb injectors? Was the MAF calibrated for the 19lbers or did this come on the swapped engine? What year is the engine out of?

[5150coupe]

using 19lb injectors and maf sensor is calibrated to 19lbs as well. not sure what year the engine is from.

i tested the car again today and unfortunately the ect, or lack of one doesn't seem to be the cause of the issue. next i'm going to check out the egr to make sure it is functioning properly. any other suggestions will be appreciated.

again...now that the issue has been happening for a few weeks now i have noticed that the issue seems to happen just a few minutes after driving down the road while cruising. for about 20 seconds i lose any throttle response, the engine boggs down, and if i give it any throttle the engine makes popping noises. i have to basically wait out this period of time till suddenly the power returns, throttle response is perfect and it seems as though there was never an issue. the issue occurs once when starting out and then seems to go away untill i stop somewhere, turn off the engine, and the car sits for ten or 15 minutes. when the issue occurs i have noticed more than once that i am giving it some gas and the motor isn't responding and then all of the sudden the car goes back to normal.

[USMC302]

Sounds like fuel starvation maybe, throw a new fuel filter in there and double check the timing. What is your Fuel pressure set at right now? Your 14 degrees advanced in timing is with the spout connector out right? When it does it next time, kill the engine immeditely and coast over ot the side of the road, pull some plugs, see if the're dry or wet....Have you tried pulling any codes yet? That would REALLY help out. I've also mentioned checking the TPS voltage again and letting us know what it is, I also suggested cleaning the mass air meter, are you trying any of these?

[5150coupe]

replaced two of the fuel filters, the one in the tank, and outside. replaced the fuel filter itself. replaced the fuel lines running from the tank to the outside fuel filter. timing is right on 14 degrees, have a perminent mark to show the correct position. tried using a new mass air meter. still no luck. not sure about the tps voltage yet. i think if the tps sensor was an issue i would have a problem all the time at certain rpms? will check though when i can get a tester. spark plugs are new and starting, idling, and 99% of the time everything seems fine. i think the issue would occur all of the time if the spark plugs were and issue, but i will check for moisture when i get a chance. question, i though at first the issue was heat related, but in the morning the engine is still cold when i have problems. it almost seems more like the amount of time from starting the car to getting a few minutes down the road, so the question is how could time be related. just don't know at this point.:

[5150coupe]

update: the car was bogging down a few minutes after starting down the road and i stalled out at a stop sign. when i turned the motor back on it ran perfect, so i tried this again several times. each i was going somewhere i waited until the car started running bad and cut the engine. i then immediately started the car back up and it ran perfect until i got a few minutes down the road and the car bogged down again. i seems that the issue occurs 5-10 mins after starting the car. someone suggested that there might be a problem with the computer? again, i'm not sure?

[USMC302]

What is your Fuel pressure set at? Have you tried pulling any codes yet?

[jsnhld]

ect will effect the way a car runs to i just spent a ton of money trying to find out why my car would not idle below 2500 rpm i bought new injectors and every other sensor on the car and i had some one tell me to change the ect and ithougt the same thing and i pulled one off of an old intake and now it runs fine

[agtech]

Hi, new to the forum. I assume you don't have a fuel pressure gauge in your car. It would be a good idea to add one, even temporarily, to help diagnose. If pressure is falling off when the problem happens then obviously you would look at fuel system, pump problem, etc.

I had an '88 LX that would run terrible until I unplugged and reconnected the MAP sensor while idling, then it ran 100%. I replaced the ECU and it was fine. It seems like you could have a similar type problem. Maybe try a different ECU.