Question about 1990 Pontiac Bonneville
Engine lopes while idling, idles erratically
Posted by Anonymous on
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Posted on Jan 02, 2017
sounds like your IAC (idle air control valve) located on the throttle body towards the front of the engine held in by 2 torx screws. the iac controls the idle if the car when your not on the gas. i will post the steps to clean the iac and the passages that the iac goes into.
1. disconnect the iac connector
2. remove the iac
3 clean the iac pintle valve and check for wear
4. clean the passages that the pintle valve sits in (usually carbon build-up in there, you may need to remove the air intake tube and air filter box to get to the passages in the throttlebody)
5. if the iac looks ok and the passages are cleaned re-install and put everything back
6. start car and see if it idles like normal when warmed up. you may need to give it a few tries for the iac to re-learn its proper position so give it a few warmup cycles
7. if it still stalls check for proper operation of the iac via ohming out the connectors (if you look it up on google you will find the specs at which the iac is supposed to operate)
8. if the iac is working properly, check for vacuum leaks on the intake manifold and vacuum lines.
9. if no vacuum leaks are present and the iac id working properly after cleaning have a shop check the ecm (engine control module) for a bad circuit board, i've seen that haoppen as well
hope this helps!
Posted on Feb 17, 2009
SOURCE: engine idle
dirty intake throttle valve and air bypass idle speed control motor. ttry the following.
Here is the most common cause of surges and stalls at stops and low erratic idle speed and rough idle, it is the idle speed control air-bypass valve and throttle valve (IAC for short), they get full of gunk over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.
Posted on Mar 15, 2009
spark plug gaps are very critical on computerised cars!! [some wont even start!]
distributor module may be breeaking down as temp rises they fail!
otherwise do compression check as it may have valve problems
also check plug leads & injectors aswell as the fuel pump pressure [ could bestarving for fuel]
Posted on Jul 18, 2009
that code is an engine misfire. try changing the plugs and wires. if that doesnt work you may have to change the coil packs.
Posted on Feb 23, 2010
Tips for a great answer:
It can be issue
with IAC( idle air control valve) causing the problem.
are many other possibilities causing these idle issues. Engine idles rough.
are few help links with solutions to troubleshoot such idle issues.
suggest you refer the link below and follow
its troubleshooting details:------
the link below:-----
Cold start problem and vehicle shudder around 2500 to
details will help.
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