Idles then dies when SPOUT is in

[btroppmann]

Hi everyone

1989 Mustang LX 2.3 non turbo hatchback.

I am working on this engine which was recently rebuilt. The engine has a stumbling idle, engine quits in about 30 seconds. The engine runs well at partial throttle to WOT. When the car starts it idles at 1500 rpm for about 15 seconds, but when it kicks down it stumbles and within a few more seconds it stalls.
If I can get this idle problem licked, I'll have this car back on the road

Last week I set the base timing on the car with my new timing light (which does NOT have an advance timing feature). It is spot on 10 degrees BTDC, which I set when the SPOUT plug was pulled out. When the SPOUT is pulled out, the car idles perfectly around 900 rpm.

However, when SPOUT is back in, the engine idles around 30 degrees initially (runs ok here) but when the idle kicks down the advance is around 20 degrees and thats when the stumbling and dying starts. I played with the throttle to confirm the computer was adjusting the timing advance, which it was.

Can anyone suggest what the problem may be. Here is a list of things I have checked and confirmed:

- timing marks on cam and crank line up perfect, new timing belt.
- new 02 sensor
- new EGR valve
- KEOE tests pass. Have not tried KEOR because it won't run continous long enough for the test.
- tps is in range - .98v at idle and 4.65 at WOT, with steady increments
- I reset the computer (by pulling the neg battery cable for one hour) after checking and setting the tps
- vacuum at the tee is 17 in HG. when it stumbles it drops to 12 suddenly and bounces between 12 and 17 until the engine quits.
- new fuel filter and fuel pump (yes I am rebuilding this car)

Thanks in advance for any ideas,

Bob

 

[ethangsmith]

Some things to check:
1. Make sure there are no vacuum leaks.
2. Ensure that there is no vacuum to the EGR valve at idle.
3. Maybe the MAP/BP sensor is bad?
4. Check the throttle stop screw and make sure it is at minimum making contact when the throttle is closed
5. Check the PCV valve to make sure it's rattling and not just stuck open.
6. Being a speed-density fuel injection system, it may have to relearn idle. Maybe two-foot it around the block a few times and see if it starts to idle.

 

[btroppmann]

Hi, thanks for the suggestions.
Confirmed that vacuum is zero at EGR valve at idle.
Also confirmed that the throttle plate comes to rest against the screw.
Drove it around about 5 miles today, problems still persists.

Not sure what the best way to check for vacuum leaks is. I pinched off various hoses between runs (brake boost, etc.) but no improvement.

I did notice the PCV valve was a bit oily, I tightened down the band clamp but sympton persists. The car starts every time and runs great (for about 15 seconds) when the stumbling starts. Help?

 

[ethangsmith]

If you haven't, I would try replacing the ignition module. Sometimes they act up like that. I would maybe try pulling the codes again (just remember, everytime you disconnect the battery cable, all the codes are erased again until the car goes through at least 1 warmup cycle).

 

[btroppmann]

I will run the KEOE again and I will try to do a koer, I will post the results shortly.
I did check the PCV valve, its rattling nicely. I've will also do the test on the MAP sensor and post that result too.

I was driving it around a bit today. Always starts fine, but it died on me four times while turning. accelerating and cruising are no problem, but with the idle that way it is the car is not driveable.

Bob

 

[btroppmann]

Ran the KEOE again, this time I got a code 22. Testing the MAP sensor now...
Bob

 

[btroppmann]

I had a look at the MAP sensor
First off it holds vacuum ok
vref was at 4.54v which I assume is ok
At KOEO the reading betwrrn sigrtn and signal was 2.5v, and did not vary if I applied vacuum to the sensor. My shop manual says 1.5v is the max value.
I assume the sensor is bad, I'm off to get a replacement - I will post the results
Bob

 

[btroppmann]

Replaced the MAP sensor, did not fix the problem. Whats next, bad gas? I'm running out of ideas here. Could it be the motor is still "tight" from the rebuild? Starts right away, fast idle is fine, but it dies at kick down. I tried adjusting the base timing to 8 degress BTDC, the problem persisted.

O I also tried idling with the SPOUT out again - ran for 30 seconds then died.

Got p*****D off at it and worked on my motorcycle instead. Tomorrow I'm going to erase the codes and run KOEO again and see what I get.

Oh ya, coming out of the store I saw this beat up crappy looking 2.3 notchback in the parking lot, owner was waiting in the car and it was running. It looked like crap but it had the sweetest idle you could imagine, almost made me cry... I'm not giving up until mine sounds like that.

Bob

 

[ethangsmith]

This is really starting to stump me now. It really points to a malfunctioning sensor, the idle air controller, or a large vacuum leak. But, it's tough to tell. If you put your foot on the gas and hold the rpms up when it tries to kick down, does it still run? Does it misfire?

 

[btroppmann]

Yes if the idle kicks down and starts sputtering, then if I press the accelerator, the engine revs up with no misfire. If I held my foot on it and run it at 2K rpm it would run all day.

Replaced distributor cap and rotor today, no effect.

When I reported the Map sensor issue earlier, it was because I was misinterpreting the spacing in the KEOE messages (oops). MAP sensor is fine, and KEOE passes.

So I did tried a KOER test today (a couple times). The motor would stall during the part of the test where it goes to low rpm. But it did spit out these codes:

34, 13, 77

13 and 77 are because the test never finished, but its reporting 34 which indicates an EVP/PFE/EGR issue.

Last week I installed a new EGR valve because the old one, despite efforts to clean it, would not seal at 0 vaccum. But the new valve did not include the sensor, which I swapped from the old EGR. I believe that senosr is the EVP sensor.

Well, with code 34 I got out the shop manual again. vref was 4.97v, fine. The EVP sig/sigrtn voltage reading was .46v, which according to the manual was in spec. just for fun, I put my vacuum pump on the sensor and put 18'' to it, the voltage climbed up to around 4.5v. According to shop manual, the sensor is fine.

However, EEC thinks I have a code 34. Any ideas?

TIA
Bob

 

[btroppmann]

I decided to redo some basic checks as well.

Fuel pressure is steady at 32psi

Compression test results are as follows:
Cylinder 1: 213 psi
Cylinder 2: 229 psi
Cylinder 3: 229 psi
Cylinder 4: 230 psi .

This is a rebuilt motor with 40 miles on it.
I did the compression test with engine warm, spark plugs out, and WOT.

Spark plugs appear whiteish/tan. All four plugs appearance is the same.

Bob

 

[Distortion 5.0]

My 93 did something similar to that when I first got it running.
It would cut off like that at low idle. My first repsonse was to crank down the idle screw so it couldn't drop that low. It wasn't a fix, but it did get her driveable.
I later replaced the IAC with one from a different car (not the same part at all)
and that stopped the problem. I honestly can't say if that fixed it or just tricked the EEC because it was a different part number, but it worked for me.

Beyond that I have no idea.
These little cars can be your best friend or most hated enemy.
Good Luck!

 

[ethangsmith]

I too had to replace my EGR valve when I bought my 88. It had a hole in the vacuum diaphragm. Interestingly, the new valve, after installation would set a code 34 and I would stall occasionally. Sound familiar now?? Just remebered this while reading your response. The culprit: The valve tip was not seating completely shut in the bore because it was a new valve and really tight, thus letting some exhaust gas in at idle and also setting a code 34. A quick thing to try would be to put your vacuum gauge on the valve and pump it up and then let off the vacuum. Listen and feel for any binding or sticking of the valve. Had to work mine for about 10 minutes till it started seating correctly. With tanish white plugs, you're burning lean, so that would indicate a vacuum leak or fuel delivery issue. How old is the fuel pressure regulator??

 

[btroppmann]

Thaks for the responses guys,

I picked up a new IAC today and I will install it tonight. Based on the lean running appearance of the plugs I am thinking the IAC is not sealing properly and is allowing more air in than the EEC expects, therefore leaning the mixture. I did pull the old one off and it was full or crud. I tried cleaning it but you just can't get it there good enough.

Before I installed the new EGR I gave it the "blow" test and it was sealing very well.

I will post my results....

Bob

 

[btroppmann]

The update is that I am still having the problem.

I did eliminate the cause of my code 34 - it was the EGR vacuum regulator. It was frozen, and did not supply vacuum to the EGR valve when the EEC called for it. Found a junkyard replacement for the solenoid, cleaned up that code.

New wires, new air filter, KEOE passes. When I run KEOR, it dies when it tests for low RPM.

I pulled the battery cable for a while to reset the computer, then drove it around for a while. When you start the car, the engine runs smooth, even if you rev it there is lots of smooth power. But when the idle kicks down, it starts running rough - if you rev it then its rough at 2k, at 3k, and so on. If you shut it off and start it again right away, she runs smooth again, until the idle kicks down.

Any ideas?

Bob

 

[ethangsmith]

Did you get the new idle air controller on there? You've officially eliminated the EGR system now so you'll have to start looking elsewhere. A gunky, dirty, worn out, or old idle air control valve would cause similar issues.

 

[btroppmann]

Yes, replaced the IAC with a new unit. While I was in there, I cleaned the gunk out of the TB and off the throttle plate.

 

[ethangsmith]

I hate to say "When all else fails, replace the computer.", but, with as much stuff as you have tested, if you have an extra computer lying around (or can grab a few at a local junkyard), I would try that. Oh, not sure if I already asked, but is the camshaft in sync with the crankshaft? Easy to check, just rotate the crank to TDC and pop the rubber plug out of the timing cover hold and see if the little trangle on the cam gear is pointing at the center line of the tab on the inner timing cover. A cam that is a tooth or 2 off can cause similar issues.

 

[btroppmann]

yes I did check timing : camshaft pully triangle lines up with TDC on front pulley and distributor pointing to number 1.
I'll go back and check if the car I got the egr solenoid from still has the computer: it was the same model year.
When I drive it it bucks a lot in 3rd gear, some in 2nd and 1st
Bob

 

[cjones]

have you checked the MAF sensor??

a sensor reading is probably bad, the car seems to run fine in open loop but runs bad in closed loop.