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Surging idle in Park only........

black dawg said:
Have you checked timing?
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I just put in a new distributor last month because the old one looked as if it had been thrown in the ocean for awhile. I set timing at 4*, (where I've had it set for 4 years), and when I tightened down the hold down, it was right on the money and the mark was rock steady never bouncing around.
 
I had a similar problem I fought and it ended up being I had plugged my vent tube that ran to my vapor canister when I did the work on it. So when I had to put a new pump in I figured out what that line was for and hooked it up, worked fine ever since. Could be something to look at, also your vapor canister could be malfunctioning. Just thoughts
 
Just an update:

...this afternoon after driving it around all over Hell's half acre, it idled nice and steady in PARK while I was at the bank and again when I got home. Then tonight my wife and I were cruising around finishing our Christmas shopping when I pulled into Burger King. The damn thing was surging so bad I thought it was going to stall out and the CES light came on.

I shut it down and checked the codes and it came up code 44 again. I started it up again and it ran fairly steady with just a slight surge. So I have made up my mind that I am just going to drop the tank and check/replace the fuel pump. At this point, it's the only thing it can be. I just hope it doesn't drop below 0*. :doah:
 
Interesting situation. We have been having this issue every now and then with the 5.3 in the Avalanche. not nearly as common as you are having it, but every so often, I'll pull in somewhere and when the idle drops when letting off the throttle, the engine will start to surge unless I'm on the throttle.

If I let it continue to surge, it usually just dies, refire the engine and it acts like nothing was wrong.

Has never thrown a CEL code, being it's OBD2, I'm planning on hooking up a laptop to it to see what sensors are reading correctly.

Sorry I'm not adding any ideas to your post to help you out, and it's a totally different engine and computer system, I just thought it weird that they sound very similar.
 
Well this has been driving me crazy for 2 years now. It's never been anything but annoying but last night I finally snapped.


It's times like these that makes carbs seem like a perfect choice but then I figure that's not the answer either.
 
Man, you have the same problem I HAD. Turned out to be EGR valve. I had replaced one, and the problem returned and finally pulled the "new" one off and it had a piece of carbon stuck in the valve. Cleaned that out and have had no issues since.
I had replaced the distributor, coil, had the throttle body cleaned and flow tested, replaced fuel pump and filter and nothing helped till I pulled the EGR valve the second time.
 
Sounds like egr to me too. I know you replaced it but carbon builds up quick sometimes. Easy to look at and clean again. If its stuck the engine can surge like it has a vacuum leak.
 
We can assume when you rebuilt the tbi you replaced the fuel pressure regulator diaphram and spring?
 
blazer74 said:
We can assume when you rebuilt the tbi you replaced the fuel pressure regulator diaphram and spring?
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It was included in the rebuild kit. So now I am getting a constant code 44 and even when it is surging and you put your foot on the gas to try to help it out, it surges until you hit about 2000 rpm's. :dunno:


I almost T-boned a lady who blew through a STOP sign last night. It was everything I could do to keep from hitting her going 40mph. Now I kinda wish I had hit her so they would have either fixed it with her insurance or totalled it out. :mad1:
 
Have you actually checked fuel pressure with a gauge? Disconnected vac to egr valve? New O2 sensor could be washed, How about the spring for the pressure regulator was it the same size as the old one.
Possible problem with the cat, disconnect it see what happens.
44 lean. Try capping off evap vac source at engine and leave gas cap loose.
Is it still ok when you first start it?

At this point Id try anything when weather permits, Last thing you need is to have an accident because of it. Id be at all out war with this thing by now!

Good Luck:confused:
 
The fun never ends! Driving down the road this morning the SES light comes on. I get home and check the codes and it's giving me a code 32 and 44.

It's telling me, (like you guys have said) it's EGR but I have tried 3 different ones and 2 different EGR solenoids with no changes. :dunno::doah:



WTF is going on?
 
Error 32 is an EGR test. After it meets qualifiers like above 45 MPH and inbetween certain MAP readings it will open and an INT change happens. It must be greater then INT change to pass.

Some bins are 4 and some 6 and some?

If you have modified engine or dual exhaust the INT may not change as much as needed, so it fails!

There's also differant EGR valves, and bad ones...
There are 2 types of EGR valves. TBI uses a Negative pressure EGR, and has an N in the part #. Using a P (Positive) part number will cause EGR codes and other strange behavior in TBI trucks.

http://www.gearhead-efi.com/Fuel-Injection/showthread.php?485-87-95-TBI-EGR-code-32&highlight=EGR%2A

I've added the paremeters in TunerPro XDF so these changes can be made and pass EGR test without turning it off.

Error 44 02 lean would still have to check fuel pressure first...
 
Hey guys....just a quick update on this.


I got through the holidays and the wife and I got out taxes back so I had a friend of mine look at the beast in his shop. He checked the thing over and he told me that all of the systems, EGR, TPS, MAP, etc., are working just fine.

He went on to check the fuel pressure and he told me it was "a little weak on the pump side and really weak on the regulator side". I replaced the regulator and ordered a Carter fuel pump and strainer from Rock Auto yesterday. It should be here by next Saturday I hope, so my tank is in the process of being dropped this week so I can get it running again by next Monday.
 
He went on to check the fuel pressure and he told me it was "a little weak on the pump side and really weak on the regulator side".
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You can take a reading at fuel filter as most gauges are set that way or on inlet side of regulator. Both should be same pressure, closer to 13 the better.

Return side should be 0...
 
eagle mark said:
You can take a reading at fuel filter as most gauges are set that way or on inlet side of regulator. Both should be same pressure, closer to 13 the better.

Return side should be 0...
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Good to know...

I can't remember if he gave me any numbers on what the pressure really was, but when he said it was weak and he suggested I change it, it was enough for me. He quoted me $350 to do it but there ain't no way in hell I'm paying that as long as my arms are still functional.
 
Do you have headers? Do you have any exhaust leaks? If you do have headers, where is your O2 sensor located? Have you been able to monitor your O2 sensor voltage swings? It really does not sound like a fuel pump issue to me, especially if it has been ongoing for 2 years and it runs fine at higher loads and engine speeds.
Get a cheap laptop and data cable. It will save you a ton of money in the long run. My laptop is over 10 years old and does the job perfectly.
 
same problem

i'm having similar problems with my 91....i quit driving it last year, couldn't figure it out....it has headers and a cam specific to tbi...it ran good for a year or so.....
 
Keitha said:
Get a cheap laptop and data cable. It will save you a ton of money in the long run. My laptop is over 10 years old and does the job perfectly.
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That is really great advice. There are good cables for cheap here:
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?1592-Support-The-Forum-Buy-ALDL-Cables!

I've built the data acquisition file and bin definition files for TunerPro RT for these 1987 to 1992 trucks which are free!
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?304-1227747-ECM-Information-42

TunerPro RT is free to use, but please pay the $39. so he keeps making updates! It's comparable to the $899. software but has more capabilities. Also works for many vehicles and now starting newer OBDII stuff.
http://www.tunerpro.net/downloadApp.htm


blazerz said:
i'm having similar problems with my 91....i quit driving it last year, couldn't figure it out....it has headers and a cam specific to tbi...it ran good for a year or so.....
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Well I guarantee it never ran as good as it could with a tuned chip for the upgrades! But if it went bad all of a sudden it is a mechanical issue. Most of which I can find with data logs from TunerPro RT. Some things in logs just point to which mechanical issue, like an error code, or readings indicating low fuel, vacuum leak etc...

For anyone interested I will go over your logged data! Just post up a thread in the Injection Section. Without a log it's just educated guesses and basic mechanical inspections.
 
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