I have been chasing an idle problem. Autozone did not find any codes the other day when I had them check but now my check engine light flashes when I accelerate the truck. It seems like it will flash as long as I am in the throttle.

My question is why would the check engine light flash while I accelerate?

I have change fuel pumps and all of the sensors except the MAP and the coolant sensor for the computer. The timing chain only has about 5 degrees of backlash. I even installed a new throttle body. I haven't change the dizzy yet and I can't find a vacuum leak either. The TP has .83mV at rest. All the ground connections are good as well.

The truck will run great and idle great then out of the blue the truck will not idle and starts searching. It may clear up or it may stall.

I also unplugged the vacuum line to the tranny with no change and I did the same to the PB booster with no change.

 

What year is your truck? Even if the check engine light blinks, it should store the code in the computer. TPS should be between .9 and 1 volt if I remember correctly. You can test the MAP sensor with either a volt meter or a tachometer, depending on which one your truck has. There may also be a wire getting pinched when you push the gas pedal and is shorting one out and causing the CEL to come on.

 

I have the exact same problem on my '90 f-150...but it usually only does it when the truck is cold, or when its cold outside....when i get on the throttle the check engine light will blink a couple times........been doing it for years...but it idles great, im thinking a short like epncsu said.....but i dunno

 

LoL , my 88 f150 4x4 does the same thing for the last 3 years. I also have a big power loss. So I'm getting my exaust done i think my cats are plugged. I hope that fixes the light. It runs great besides the lack of power.

 

Pull the codes, the computer should store it. I personally don't trust Autozone.. You might want to read this..

powerz69 - Have you pulled the codes?

 

No, but after that link you gave i'm going to try. I don't really know what to do. I guess i'll probe around with the test light LOL.

 

I forgot to post what year my truck is. It is a 89 351W.

Last night I bought a new MAP and coolant temp sensor for the computer. Now I have replaced all of the sensors and I am thinking of buying a new computer. They only cost $90 at autozone and the guy that works there feels sorry for me because I keep buying parts so he has been giving discounts. Last night was 20% off a $100 purchase. I also replaced the cap and rotor button since I replaced the wires the other.

I didn't get to drive the truck yet so I am not sure if the engine light will flash or not. Since my problem of random stalling when I slow down started the check engine light would never come. PEP boys couldn't find anything either. I was out of town when this happened.

The check engine light started coming on after I had a problem with the truck not idling at all and running rich. Since then the engine light flashes when I accelerate. I may have damaged the cat with the extra fuel in the exhaust? The fix for the running rich seemed to be a air line came off of the air pump and I also found the ground wire from the battery was loose. I fixed those two things and it doesn't run rich anymore.

I will drive to work this morning and post what happens with the new MAP and coolant sensor installed. The truck did idle alot better last night. I could get it to search for the correct idle by stabbing the gas but it never died. Then again things are always different the next day.

Here is a link I used for codes http://fordfuelinjection.com/selftest.html

I think I did find codes and when I took it to autozone they didn't find any? I will check for them myself again tonight.

 

Well the truck didn't stall while warming up in the driveway which yesterday was the first time the truck ever stalled while warming it up in the morning. I could hear the motor searching for the correct idle a few times but never stalled.

The check engine light still flashes when I accelerate but it didn't flash like it was yesterday. I could only get it to flash a couple of times. I could do it a will yesterday. I am sure this doesn't mean much but its hope. Oh, I have great power still when the light is flashing. No power loss yet to speak off.

Once I started driving the truck it ran great never stalling or searching for a good idle when I would stop.

I need to check the connection of the harness and the computer. If I don't find anything there I have two things to change and they are the dizzy and the computer. If they don't fix the problem I don't know what will. I will check for codes first. I just wanted to drive it today since I had the battery disconnected yesterday while installing the new MAP and coolant sensor.

I have a hard time believing it's a vacuum leak for two reasons. One I have checked and the other is the problem is so erratic which makes it hard to pin point. The truck does seem to be running better once it warms up which is the opposite of what it use to do.

Can anything from the air pump set up cause anything like this? I can hear the air passing through the pipe that connects to the back side of the heads. I removed it and I can blow air through it but it makes a funny noise when I do. It acts like a check valve which I am sure it's supposed to.

 

I almost had a fire start in my truck bout 3 months ago b/c of the wiring harness going bad....i opened it up(the part that goes between the firewall) and it was all black.....my brake light had been staying on all the time and that was some of the prob...so i had to get a new harness for 100 bucks....your prob might be somewhere in the harness

 

I am going to the junkyard this Saturday. They had a late 80 model truck with a 302 in it. I am going to remove the harness from it and maybe give it a try. But first I will check the connection at the firewall.

When you say between the fire wall what part are you refering to, the computer connection?

I have seen a couple of ford trucks that have had cab fires in the junk yard. Not a good thing.

 

Still have a problem with the random searching but not nearly as much as it use to. For the most part I can just tap the gas once and the truck will keep on running but the rpm's go above 1k and then settle down.

I replaced the EGR valve and the truck does perform better. After the replacement code 34 was gone but now I get code 35 which is the same but add PFE to 34 and you have a 35 code.

I checked the voltage on the EGR sensor and it as high. So I ground the pin down until I got the mV reading in the middle of the range. After this I still get code 35 but the check engine light isn't flashing as much as it use to.

I tried the old MAP sensor and nothing changed

I am going to try the old sensor from the EGR valve tomorrow and see what it will do.

The truck is running very well compared to before. I wouldn't be afraid to drive it any where now but I hate not having something perfect.

 

I had rough running, idle and dying at red lights a few years ago on my 88 bronco. I took it to one of those chain store fix it shops. They didn't find any codes for this problem. When I got home and complained they told me to try cleaning the Throttle Position Sensor with carb cleaner. I didn't have any on hand so I used WD-40. It worked for a while. I kept cleaning it with carb cleaner and WD-40, I don't know which I used last. But the problem was fixed. I think I have had to do it again a couple of times in the last few years. The TPS on an 88 is on the right side of the throttle body. Remove the throttle body inlet hoses coming from the air filter. Remove the two screws and pull the piston out of the cylinder. This is tight. Just spray off the piston and cylinder and wipe. It's not real easy to get the spray into the cylinder.
I read somewhere that you can find vacuum leaks by taking a stethescope and remove the diaphram or rod from the end of the hose. Go around the vacuum lines and gaskets with the open hose. I haven't tried this yet. Good luck.

 

All of the sensors have been replaced with new ones. You name I have changed it. I even tried two IAC sensors with no luck.

The TP is new and I even open up one of the holes in the TP sensor with a 1/4 drill so I could adjust it closer to 1.0 and I ended up at .98mV. I had a reading of .83 before the adjustment.

Now the truck seems to idle in gear with no problem but when I put it in gear it will start searching again. Once I start driving the truck this problem goes away. Its only been a couple of days so its hard to say reaaly working and whats not and when. But it does seem to run very well once I have beend driving it.
I may try the other IAC sensor and the original sensor on the top of the EGR valve and see what happens since my problem has changed from one thing to another and I have changed everything who knows what I have now.

thanks bob

 

My check engine light was flashing when I bought my truck and it went away after I replaced the cracked exhaust manifolds (the extra air triggered an Oxygen sensor code). Since you replaced your O2 sensor with all other sensors, it is probably still ok, so check the memory codes (not the current codes). is there an O2 code in there? So carefully inspect your exhaust manifolds, most of them are cracked by the time they reach the age of your truck.

 

I get no 02 codes only code 35. The first check shows up as 11 and then it goes into the second check and thats when I get code 35.

This is with me pulling the codes by grounding the wire to the neg side of the battery.