Engine trouble on the DD - F-Body Road Racing and Autocross Forums

My daily driver is an 88 Buick Park Ave. Lately, I've been having trouble with it running right when the engine is hot and I restart it. Almost seems to be vapor locking, but it's multiport fuel injection. Ocationally when this happens, I can bleed some "air" or maybe fuel vapor out of the schrader valve on the rail which sometimes helps, sometimes not. It starts, then idles like it's missing badly and the engine won't rev up. So far, I've been able to coax it into working and getting me where I need to go, but I at a bit of a loss as to why this is happening all of a sudden (the last week or so). The weather hasn't been too bad lately and it was certainly hotter earlier in the summer and it ran fine. It seems OK while I'm driving and after it's been allowed to cool down all the way.

The recent maintenance includes:
new fuel filter
new plugs
new coil packs and igniton contol module
Removed and cleaned injectors (really were pretty clean to begin with)

My ideas:
fuel pump is low on pressure allowing the fuel to vaporize in the rail while sitting after driving
Bad presure regulator not holding the pressure up while sitting after driving, or sticking not allowing the vapor to exit and return to the tank.

Any insight or ideads would be appreciated.

00 SS View Member Profile	Aug 15 2011, 11:23 PM Post #1
Experienced Member Group: Advanced Members Posts: 1,197 Joined: 13-February 04 From: Hudson, Colorado Member No.: 197	My daily driver is an 88 Buick Park Ave. Lately, I've been having trouble with it running right when the engine is hot and I restart it. Almost seems to be vapor locking, but it's multiport fuel injection. Ocationally when this happens, I can bleed some "air" or maybe fuel vapor out of the schrader valve on the rail which sometimes helps, sometimes not. It starts, then idles like it's missing badly and the engine won't rev up. So far, I've been able to coax it into working and getting me where I need to go, but I at a bit of a loss as to why this is happening all of a sudden (the last week or so). The weather hasn't been too bad lately and it was certainly hotter earlier in the summer and it ran fine. It seems OK while I'm driving and after it's been allowed to cool down all the way. The recent maintenance includes: new fuel filter new plugs new coil packs and igniton contol module Removed and cleaned injectors (really were pretty clean to begin with) My ideas: fuel pump is low on pressure allowing the fuel to vaporize in the rail while sitting after driving Bad presure regulator not holding the pressure up while sitting after driving, or sticking not allowing the vapor to exit and return to the tank. Any insight or ideads would be appreciated.

wrencher View Member Profile	Aug 24 2011, 04:34 AM Post #2
Member Group: Advanced Members Posts: 136 Joined: 4-September 10 From: Chicagoland Member No.: 20,108	It's possible the CKP (crank) sensor has a fault. As well as the igntion module. But I am @ a loss for a way to tell you how to diagnose it. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/sad.gif) The only way I test those type circuits is with a osillscope, not a piece of equiptment in everyone's tool box. That intermittant of an issue it could be a connector or a sensor issue itself. The CKP is a hall effect sensor (shutter wheel on balancer) The adjustment of the sensor is important, but as long as it's not hitting the shutter wheel & getting damaged it's not real likely it's causing it. The CMP is obviously a magnetic pick up. The CKP & CMP basically share power & ground. The ignition module communicates these signals to the ECM.