Hi,

1994 Buick LeSabre Custom with 101,000 miles. Car has constant rough idle. In hot weather car will begin to surge and stall during or after idling for a few minutes. Difficult to restart. Stalling is intermittent. No stalling in cooler temperatures. Today'* temperature was about 84.

Car was purchased at approximately 70,000 miles. Since the numerous parts have been replaced including: ignition coils, spark plugs, wires, ignition module, PCM, EGR Valve, PCV Valve, Camshaft Sensor, Crankshaft Position Sensor, and Alternator. In addition, brake fluid flush, transmission flush, coolant flush, and oil changes. Good quality fuel is used. Every time something is replaced it seems to fix it for a while before it begins stalling again.

The handheld scanner codes are:

PO755 F31 Transmission Solenoid Failure
PO300 Misfire Signal Misfire Detected

Some information from the handheld scanner:
Fuel Trim: 135-141
EVAP: 20%
Coolant: 215
EGR: 0.8
KS: 119
IAC: 59
Idle: 825
Inj. pw/ms: 3.9-4.7
ST Fuel Trim: 128-133
MAF gr/*: 5
IAT: 157
Spark Adv: 6-18
TPS Sensor: 0.53
Trans Temp: 204-206
02S Crosscents: 1

I appreciate any and all help and or suggestions.

It'* running rough because you have a random misfire. How old are the spark plugs, spark plug wires, and coils? Make sure the plug wires are on near the wiring harness.

Hi,

Thanks for the reply.

This car has idled roughly since I bought it from the dealer. It has been to numerous dealers and shops and parts get replaced yet it hasn't fixed it.

The spark plugs, wires, and coils were replaced last year. The wires again a few weeks ago.

This has been a problem for years and nothing fixes it and a lot of money has been spent on it.

When you take the plugs out how do they look? Color etc. Take pictures and post them.

Hi,

Thank you for the response.

I replaced the spark plugs with new AC Delco plugs. What was in there was platinum and they had some carbon on them. The idle speed improved and the power improved but the rough idle continues.

I had the car on the scanner for quite a while today, I let it run and warm up. After the car warmed open #4 began to miss, then #3 and #5. It wasn't constant.

There has been a whistle from under the hood and I decided to check for a vacuum leak. The vacuum hoses were replaced last year with new ones but the whistle continued. The whistle is near the EGR Valve and the vacuum hoses. It turns out that the metal hose that goes into the upper intake manifold is the cause. If I press on the metal hose the noise stops and the idle changes.

The car had a new upper and lower intake manifold put in by the dealer a few years ago but they didn't replace any of the EGR related parts.

My question is, what is that metal pipe called that is attached near the EGR and goes to the upper intake manifold? The hose is metal and attaches to a plastic part next to the throttle body. How do I remove and replace it? Does it require gaskets and if so, can I remove it and replace the gaskets or must the metal hose also be replaced?

What are your thoughts on this? I appreciate your advice.

Thank you.

That'* the EGR tube. Yes, you will need to replace it. I believe www.rockauto.com has them. You just remove the 10mm bolt on each side and pull the tube off.

Here is a link to the spark plug photos

https://www.gmforum.com/members/indplsin72-38130-albums-spark-plugs-452/

Here are pics of the EGR hose. I'm not sure if the leak is at the plastic connector at the upper intake manifold or the metal plate that connects to the EGR mounting bracket.

How do I remove the plastic connector?

When installing a new hose, does require any gaskets or sealants?

Thank you.

Apparently I cannot post pics so here is a link to the EGR hose connector.

https://www.gmforum.com/members/indplsin72-38130-albums-egr-hose-453/