This is the same ERRATIC ROUGH IDLE problem where I replace the EGR valve, IAC valve/solenoid, EVR solenoid with no improvement. This is on a 90 Bronco 351 w/ MAF conversion. No check engine light. MPG OK . Performance on freeway and hills OK. Has been running good (65k miles) until a bad alternator and battery was replaced. Alternator had a bad bridge diode and non-operating field coil relay. Tech said this could do harm to primary circuit components.
Rough idle is initially 1200 rpm at start then comes down about 200 rpm and oscillates up and down 100-200 rpm's.

Did a KOER code scan and got these codes which has me lost because they are
not failure codes of component:

15 ECA keep alive memory not working? open in the harness?
32 EVP sensor low voltage I checked the output w/ ohm meter and it varies as pintle moves. it also holds vacuum, no leaks.
38 ITS idle track switch open I don't think it has one, can't find it. Where is it located?
41 EGO signal voltage always low (lean) doesn't switch
53 TPS voltage too high
66 MAF sensor voltage signal too low

What do the above codes indicate?

What do you do with too high or too low voltage conditions?

Do I have a Bad ECU? Should I suspect Open or shorts in the MAF conversion harness?

Any help appreciated!

Ron

 

Hmmmm, if you find the answer to this one I'll very interested. I just bought an 88 F-150 XLT Lariat about 2 months ago. 98k miles on it (thought it could have possibly turned over once but there were lots of records in the glove box and that seems accurate) my oil pressure gauge would drop to nothing when I was slowing down ( about 500 rpm, instantly lost pressure.) So we changed the oil pressure sensor. No luck. Hooked up a mechanical oil pressure gauge and found that we really didn't have much for pressure. Ended up rebuilding the motor. Was VERY worn....just got done putting it together and it runs great except a few things.....starting it, the rpms kick wayyyyy up then down, up and down until it finally dies. About the third try it will stay running and jumps around a little finally leveling out at around 500 rpm......And most likely not connected to that problem....my rear tank seems to be filling up my front tank.......had both tanks full and then next thing I know half a rear tank and opening my front tank it would overflow....
any help appreciated....
thank you.
Sabrina
GypsyRose31299(No Email Addresses In Posts!)

 

There is a check valve in the fuel line that is supposed to prevent one tank pumping to the other.If it fails you have your problem.Ford had some unofficial recalls on these dual tank set ups you might call a dealer and ask.Since you are pumping gas back to the other tank you may have a fuel presssure problem.Put a gauge(autozone sells them)on the fule rail and watch the pressure while the idle is jumping around.


Ron code 41 I would check for vacuum leaks and check the 02 sensor.
Code 53 check and adjust the tps voltage to just under 1.0 volts at idle.Code 66 check the maf sensor reference voltage.I would also disconnect the battery for an hour or so and then run it and recheck the codes.

Billy

 

Thanks Billy,

Code check was ran after clearing memory. Does it require repeating?

Any clues to what sensors & controls crap out when they are twelve years old?

With MAF, TPS, etc. is the ref voltage suppose to be measured with engine running or just with the key on, or does that matter?

How do you check a O2 sensor? I know how to verify the heater part but not the the rest.

The manifold vacuum measures almost 20 in Hg. at the vacuum tree. Would that indicate no leaks?

Ron

 

[updated:LAST EDITED ON 11-Oct-02 AT 05:26 AM (EST)]No but it would'nt hurt to clear them and see which ones repeat.My Haynes calls for refference voltage checks with engine off key on.To check the o2 sensor itself you need to remove it and heat it with a small propane torch and check the readings on the gray and black wires,the white wires are the heater wires.With the sensor hot and the flame covering the element it shoud read around .8-.9 volts (rich)remove the flame from the element slightly and the reading should go lean .1-.2 volts.Then with the truck running and on temp(sensor installed)backprobe the two wires again and see what the 02 reading is.If it's real lean you could have a fuel problem or a vacuum leak.with 20" vacuum you probaly don't have a major vacuum leak,but even a small leak can cause idle problems.Spray some carb cleaner around the intake and the vacuum lines listen for the engine speed to pick up signallng a leak.I would get a good manual and check all the sensors per the instructions.TPS and IAC are often the main culprits in idle problems.What kind of mass air conversion?I've heard of people having idle problems and weird codes after converting.The eletrical problem I'm not sure what that would do.Trouble shooting EEC codes can be frustrating.sometimes other problems will cause codes on sensors that are not bad,like a vacuum leak.I had a bad rich condition and idle surge caused by a failing fuel pressure regulator.
I checked the fuel pressure several times and it checked ok,but apparently it would come and go when driving until the regulator finaly failed.I was getting egr codes,o2 codes and IAC codes.I would recomend testing the sensors and if they check out don't replace them, keep looking.you can throw a lot of money at it and still not solve the problem.Sometimes it's worth the expense to take it to a dealer and have them run a diagnostic check before you start part swapping.Most of those guys have seen all the problems before.You can still do the work yourself once you find the problem.



Billy

 

Billy,

Thanks again for your inputs.

I didn't know that a Ford dealer will do diagnostics only. What if they are wrong?

I have thrown a lot of $$ already. IAC cost $116 EGR @ $85 EVR @ $35. Some might be returnable.

The motor has 65-70K miles. I put in a new fordmotorsports short block M6009-C58 (similar to lightning block) in at 127K. At the same time put in the fordmotorsports lighting truck MAF conversion kit M9000-L58 It includes the ECM, airbox, hoses to TB 80mm MAF sensor 30lb injectors and the conversion harness. I don't believe the MAP is used now. Sequential injection seems more positive, especially in torque response.

I also had upgraded exhaust and intake heads and manifolds and a roller hyd. crane cam.

The fuel pressure is 40 psi at the rail, put in an adjustable one at time of conversion because of the 30 lb injectors. Problem is that no more adjustment left when at 40 psi and I was able to get 50-55 when it was new.

I had an alternator diode and field relay go out which hurt my one-year-old battery by damaging a cell. I replaced both.

Tech said that the alternator could have done damage (i.e., voltage spikes) to anything in the primary circuit. This has caused me nightmares about having to get a new ECM or the whole dam M9000-L58 kit in case it's not available separately.

Is there anyway to check a ECU ? Is ECU vulnerable to voltage spikes? Somebody told me to go to a diagnostic shop that has a EEC-IV break-out box ECU test set-up. They are suppose to be able to view all the inputs/outputs and make a judgment call. Know anything about this?

I do have a Haynes book and have found errors in there. Ex: the test for the EVR is to put vacuum at the supply port and it says it is suppose to hold it, if good. Not so, got a new one from dealer and it don't hold vacuum. Found out nothing wrong with my old one which I though was malfunctioning and causing erratic idle.

It has been running great for the past 70k miles, no problem w/ idle. I still have good torque in going up long steep hills. MPG is the same ~ 13-14 mpg regardless if I drive w/ AC on or do some city driving. BTW, this is a 90 EB Bronco w/ 5.8 and E4OD

I'm obviously hooked on this truck, but next time I'll get a Lexus rx300 2wd. I getting too old and I don't want to play mechanic all the time.

Ron

 

If I am reading this correctly, you ran for 60K + miles without a problem, and your alternator failed, then you had other problems, which generated several seeminly non-related codes.

That points to a single problem causing all the codes, and not the individual problems that the codes indicate. One thing that is common is that all the sensors have a regulated reference voltage applied to them. It could be that when your alternator went, it crashed the regulator in the ecu.

Try to determine what the reference voltages are to each of the sensors which indicated a problem. It they are all off, and all showing about the same voltage, then, I would say that your problem is located. The solution, however, may be difficult. If the ecu is the standard oem Ford one, you may be able to borrow, beg or buy a used one to test with. If it's a proprietary one, from the manufacturer of your conversion kit, you may not be so lucky.

Anyway, that's where I would start. If the reference voltages are ok, then some other common point may be a fault.

Hope this helps.


Winford

 

Winford,

Thanks for the heads up on the ref voltage.

I should start to measure the ref voltage at the ECU. What pin numbers would they be? I would know the voltage was correct or not at that point. Maybe the harness might alter the voltage? or the sensors themselves? Thus, I would not get the correct 5.0 v ref volts?
Is there a tolerance on the 5.0 volts?

What is the purpose of the Rev. Voltage at each sensor? For example, I measure the resistance of the two pins on the EVP (which looks ok), how is the other pin for ref volt. used?

When I found the bad alternator, it was not having the erratic idle problem. The motor was just dying when coming to a stop. Sometime after the alternator and battery were replace, I started having the erratic idle problem.

Then I exchanged the ignition module, thinking that was the problem. It may have been part of the problem. After ign module was replaced it just idles lousy, so I increased the idle rpms a bit and it doesn't die.

Also when I replaced the EGR and IAC it made the idle much worst. More swing in the rpms & at a faster oscillation and a lot higher idle speed especially on startup. Like 1500 rpm then goes down to 1100-1200. with old parts idle is 850-1000.



Ron

 

The ref voltage was 4.99. So ECU seems OK,
EVP values way off, replaced the unit with a new one.
Got 1.5 v. for TPS; replaced it and set it at 0.9 v.

Problem solved, no more erratic idle.

Adjusted idle screws on spacer plate beneath the IAC so I get 750 rpm at idle.

Disconnected the battery overnight so I could read any new codes. I suspect a bad O2 sensor cuz it smells rich in the exhaust and I got 11 mpg last run on the freeway. Was getting 12-13+ mpg. Total miles is at 192k, and I recalled replacing the O2 at 45k with a factory ford unit or NTK brand. Think I need a new one?

Then codes were re-read.

Here's the strangeness . . . . . all the SAME codes came back except the ECA keep alive voltage (15).

What's happening? Don't all the codes get dumped if I disconnect battery overnight?

Ron

 

With some years you have to turn the head lights on when you disconnect the battery. I dont know why, but it works. Also You can clear the codes by pulling your jumper out before the test has finished generating codes, and before you turn off the ignition. Try one of those and see if the codes clear. Hope this helps.

Bill