I am still working on a bad idling problem that comes and goes. Could an bad injector cause a come and go idling problem? It only gives me trouble when I am in gear and sitting still at an idle. Not all the time. The truck will idle great and then it won't.

thanks bob

 

You might want to scan for codes.......

 

Been there and done that and every sensor that you can replace has been replaced.

I do keep getting a code 35 but no one can answer what will cause a code 35 other than if possible the EGR valve. I replaced the EGR valve and I still get the same code as I did with the old one and the sensor is new also.

When I first starting having trouble no codes could be found at all. Then I got code 33 and now code 35. Some where along the line my check engine light decided to start flashing while I am driving down the highway.

No one that I have talked to thinks the EGR system would cause this random idling problem.

I am afraid to pay $80 to hook the truck to the computer and have them not be able to tell me anything. I've spent enough money already.

I have had the truck just die on me and not restart. After letting it sit for a while it restarted. Fuel pumps are new also. Dizzy is new. You name I am sure I've changed it. Any other ideas? thanks

 

I am not sure what engine you have or what year truck it is but, My 87 had the EGR codes since it was brand new. The light flickered and was on and off since I bought it brand new with 1 mile on it. I was told by the Ford shop where I bought it that the computer sample rate on the EGR was to fast and I would never get rid of the problem. I removed the light and checked codes at every oil change, it never created any problems. The truck has ran the same for the past 16+ years and 170K miles. Well that is until I just put a brand new Mustang short block, mass air conversion and many other parts on.

Since your not getting any other codes I would change the TFI module on the distributor, check your timing, change the fuel filter, clean the IAB (idle air bypass) and check for vac. leaks. Make sure "all" battery wire connections, - and + look good, good plugs, wires, cap and rotor. I always run 92 octane fuel also. Running the lower grades always ended up giving me starting troubles every once and a while, where it wouldn't start the first time, pinging and knocking ect... When I fill up I usually only put in 10-12 gallons so it is worth the extra dollar or so to run the higher octane to me. It also helps a bit to run the right weight oil for the season your driving in. Good luck.

 

I always forget to mention what year my truck is. I have an 89 with a 351W with 124K miles. The truck has great power and runs out well. The plugs have looked great everytime I have removed them.

As for the things you mentioned I have done. Items new, dizzy, TFI module, egr valve, ERG sensor, IAC, TB, TP, coil, cap, rotor, wires(motorcraft), plugs, air temp sensor, coolant sensor, fuel pumps, fuel pump relay, fuel regulator, MAP, PCV and computer. I think I covered everything.

I set the timing prior to the new dizzy install but I haven't checked it since I installed the dizzy. The truck has the same idling issues either way. I have checked for play in the timing chain and I only have about 5 degrees of back play. I have checked for bad connections and vacumm leaks and I can't find any. I can hear the check valve on the tube on the back of the head pumping air when the truck warms up. Not sure that means anything. I even replaced the ignation switch on the column with a used one to see what would happen. I have watch the voltage on the EGR valve with the trucking in gear and out of gear but not under load driving and the voltage will climb to 3.8 or some where near there but the main thing is it always return to the closed volatge reading. if I removed the vacuum line to the EGR it would not change the voltage out put as much when I reved the motor.

It really acts like the IAC just won't update fast enough to the change in engine load. The down side to that is when in park I can sometimes hear a miss in the motor. Its just not as smooth as it should be. Now at this time I know I can put the truck in gear and get it to act up. Rev the motor a few times and it may go away. So thats why I am thinking bad injector or a hanging valve but I can't believe and valve would hang up and then not hang up.

 

If you have replaced the EGR, did you clean the EGR pipes as well?

The EGR pipes do get clogged up but the one that most get clogged up is where the EGR pipe connects to the Exhaust Manifold and the other end that connects into the intake port.

 

Well if the EGR pipe was clogged I don't think that would cause any problems at idle...because the EGR shouldn't be open at all then.

Looks like you have changed a lot. Have you ever tested the compression? An engine with uneven compression can run rough even if everything else is in order. It's not how high the compression is, but all cylinders are within 25% of the highest/lowest.

Also, 5 degrees of play is pretty good amount of slack for a timing chain. I would imagine that replacing it would improve your idle, but it may not fully resolve it (some people go 8 degrees before it really affects it...but if your valves are not in good condition it will affect it with less slack).

Assuming you have cleaned the intake/throttle body, it might be wise to pull the injectors and have them flow tested and cleaned ultrasonically. Granted the cost and downtime starts you thinking that you can buy a brand new set for less than $200 on ebay, or if you want a warranty, 50motorsports.com. Have you ever had a fuel related problem? Rust in your system could be a culprit.

 

I've only had the truck for just over a month now so I can't answer the rust in the fuel question. I can only say that the rear tank screen looked clean when I changed the pump.

As for clean the throttle body it's a brand new BBK TB. My old one was sticking causing the rpm's to idling around 1200 to 1400. So I thought or hoped that the computer was adjusting for the stuck TB and when it would unstick I would have an idle problem. Well the TB didn't fix it.

When I replaced the EGR valve I did not check the pipe but I can say the old EGR was very clean. The pipe to the EGR is loose at the manifold. Enough so I can move it anyway. I can't get a wrench on it to tighten it up. I will have to make a wrench I guess or remove a few things so I can get to it.

As for my check engine light flashing I read a post this morning that said to unplug the vacuum line to the EGR valve and if the light stopped flashing then the solenoid is bad. Well I just got done driving on the highway and I tried my best to get the check engine light to flash and it didn't. So here goes another $50. I have to order it from Ford. I know this won't fix my idling problem but it may get rid of the code 35 I keep getting. If it does then I have an idling problem and no codes to help pin point it.

I can borrow a set of used injectors from a buddy and give them a try. I will go pick them up as well today and give it a shot.

If and when the truck stalls as soon as I start it back up it seems to be fine like something reset itself.

 

Just a thought, but is you truck running rich or lean by chance? you mention the EGR pipe being loose (are you talking about the exaust manifold side or intake?). I wonder if you have an exhaust leak due to that loose pipe. With an exhaust leak, you not only are pushing exhaust out, but also creating a vacuum which pulls air/oxygen into the system. Your O2 sensor will read this incorrectly and have the computer adjust the A/F ratio. Just a thought.

 

The EGR solenoid did not fix the flashing light so there goes another $50.

The EGR pipe is loose at the manifold end but not loose enough to make any noise just loose enough so that I can move. I will try to get it tight.

I talked with my buddy's father who is a very good mechanic and he thinks I have a bad dizzy module even though it's new. What does everyone else think?

 

I'm gonna bet on 1 or more bad injectors. A cylinder balance test should confirm this. I believe the V8's have the cylinder balance test as part of the ECC self test. You can check it with a code scanner.

 

The only code I get is code 35 when I check by grounding out the pin. Should a run test be done? If so I have no clue on how to perform a running test. thanks

 

How low does your idle get before it cuts out? What rpm? Does the engine continue to run if you raise the idle a little? Raising the idle could be done in a couple of ways.

 

I use one of those code testers ( cost like 14 bucks from walmart ). It comes with instructions. The cylinder balnce self test only works of your motor is SFI ( sequential port ).

On older motors I used to hook up a tach and pull each plug wire one at a time , recording the RPM drop. A drop thats smaller than the rest indicates the weak cylinder. I tried this on my six but it gave me a jolt when I pulled the wire. Like something tapping my elbow. Nothing serious but caution is advised, especially if you have high power ignition mods installed.

Check the plugs too. Note if any are different in colour to the rest.

 

The truck will idle as low as 400 rpms and then go to 1000 rpm and back down again. The ranges can vary a little up or down. When it gets to a 1000rpm it will sit there for a few seconds and then come down and start searching again. If it doesn't reach 1000 rpm then it will search between 800 or lower and some where around 400.

Two things will prevent it from stalling. Me driving with two feet or putting the truck in neutral. But you can hear a slight miss still in the motor. This miss is not always present. When I hear this and the truck is in neutral or park I know it's going to act up when I put it in gear. Then when I take off from the light and drive it, it may not do it again until I shut the truck off or it may act up again at the next stop. Of course some times I can let it search for the correct idle and it will not stall so I keep driving and the next stop it idles fine again.

If I try to adjust the rpms at the throttle body it will raise the rpms but only for a little while then the computer pulls the rpms back down to where they are supposed to be. I have adjusted it back to were I was instructed to so I no longer mess with the throttle body adjustment. Other than that I don't have any idea on how you could increase the idling rpm.

The truck has cut out on me twice and not restarted until the truck had sat for maybe an hour. This just happened last week. The first time it happend I had the trucked towed in and they checked it out the next day and found nothing. By the time the truck got towed in it started and ran fine. This is my only reason for thinkinh the dizzy module is bad and I have been told that others have bought new modules and they where bad as well. but to do the same thing would be odd.