'87 TBI Rough Cold Start

[Fleetwood]

Hello! I have an 87 with a 350 TBI that really does not like to start in the mornings when it is cold. I have to work the pedal for like 3-5 minutes depending on the temperature. When it is warm it runs fine. What could be wrong? The tube that comes from the exhaust manifold to heat the air is missing but that does seem like it would cause this many problems

 

[WP29P4A]

I would check the easy free stuff first, look for vacuum leaks and check the sensor/controller ground on the intake manifold, close to the thermostat housing. On my son's truck we fixed a couple vac leaks and adjusted the idle along with cleaning and tightening the grounds and it made a huge difference in starting and idle consistency.

 

[Snoots]

Sounds like the IAC is gummed up.

 

[gmbellew]

I'd agree about the IAC and maybe the CTS or a stuck open EGR. if it is on a cold start, it is one of the things the computer is using before it gets to closed loop...so it narrows down the culprits somewhat. I assume there are no codes being thrown or stored?

 

[AuroraGirl]

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

also, clean your IAc, clean grounds, make sure your alternator is working good/good battery, consider plugging your EGR to see if the problem gets better (unplug the ocnnector and plug the hoses), use a single fuel treatment in tank, upgrade to a heated o2 sensor (its old anyway), make sure no exhaust leak.

 

[fast 99]

Those base gaskets were prone to failure. It isn't a common, but few ever think to check for excess alt AC voltage. Easy to check with a digital voltmeter and will cause all sorts of drivability issues. Also, try disconnecting the EGR temporarily. Coolant sensor would be something to look at. There is an ohm value / temperature relationship spec. and check for coolant intrusion into that connector, common problem.

 

[AuroraGirl]

Those base gaskets were prone to failure. It isn't a common, but few ever think to check for excess alt AC voltage. Easy to check with a digital voltmeter and will cause all sorts of drivability issues. Also, try disconnecting the EGR temporarily. Coolant sensor would be something to look at. There is an ohm value / temperature relationship spec. and check for coolant intrusion into that connector, common problem.

is it coolant intrusion into the connector or is it coolant ..extrusion... through the tip and then slowly into the wiring. on buick cars the coolant could make its way to the ECM

 

[Itali83]

Coolant temp sensor. Tellin’ ya

Ben

 

[fast 99]

is it coolant intrusion into the connector or is it coolant ..extrusion... through the tip and then slowly into the wiring. on buick cars the coolant could make its way to the ECM

Either way, I got the point across. Yes, the coolant can travel to the ECM. I only saw that a couple times but talking to other techs they saw it more frequently.

On the TSB PROM update, if a scanner isn't available I believe the PROM has the code on top of it. Just remove the screws to the trap door.

When starting cold the ECM does not use the O2 sensor data until it is heated up to operating temp. Doubt that would be the problem, however if it hasn't been replaced doing so is a good idea. O2 sensors get contaminated and become slow to respond.

 

[AuroraGirl]

Either way, I got the point across. Yes, the coolant can travel to the ECM. I only saw that a couple times but talking to other techs they saw it more frequently.

On the TSB PROM update, if a scanner isn't available I believe the PROM has the code on top of it. Just remove the screws to the trap door.

When starting cold the ECM does not use the O2 sensor data until it is heated up to operating temp. Doubt that would be the problem, however if it hasn't been replaced doing so is a good idea. O2 sensors get contaminated and become slow to respond.

If its never getting to temp it could be running less efficiently which is now deposits and crud in the passages. The point is that we should fix the sensor to at least be new because age and wear happen but heated would be best.
Also ,if its going into closed loop but the sensor is poisoned or inaccurate, there could issue too(just there is possibly something else, never discount compounding things esp on these old farts lol)

 

[fast 99]

If its never getting to temp it could be running less efficiently which is now deposits and crud in the passages. The point is that we should fix the sensor to at least be new because age and wear happen but heated would be best.
Also ,if its going into closed loop but the sensor is poisoned or inaccurate, there could issue too(just there is possibly something else, never discount compounding things esp on these old farts lol)

I wasn't referring to the engine temp. The early single wire O2 sensors do not have an internal heater. However, if the engine is used for short trips or has cooling system issues that wouldn't help either. Were kind of getting in the weeds here. All I am saying is the ECM doesn't use feedback from the O2 sensor during a cold start.