Idle problem after start

[COdsm]

I searched for other threads, but there are a ton of idle threads and not many seemed to match my problem.

Occasionally after starting (cold or warm) my idle will drop to around 200-300 and it sounds like it is misfiring, all around bad, so I'll give it some gas and hold it around 1.5k rpm for about 30 seconds, some small backfires (from the misfires), then it runs and idles fine.

But what's got me scratching my head is that it only happens maybe once every 20 times. And I can't seem to find any common conditions that could cause this to happen. There is no consistency to the problem, and I notice no other differences in performance.

Thanks in advance for any advice.

(FYI 100% stock 4G63)

 

[eclipsyco]

If I were you...
I would scan it first then I would replace fuel filter, spark plugs and spark plug wires, clean the injectors and check the timing!
After all that I do a BLT and a compression test.

 

[chrisgarza]

^Agreed^ eclipsyco has you on the right path. That is the cheapest route to get going. If all that fails check MAF and TPS. Although I would be willing to bet it's a boost leak. However I did just have a odd prob on a 91. Car would occasionally idlle rough after missing on boost. Turned out to be trash on the fuel pick up tube filter. Let us know how it goes.

 

[ChiTownHussla]

Sounds electrical to me

 

[COdsm]

Eclipscyo and everyone else, I have performed all that maintenance recently. Compression and BLT are all ok. The inconsistency makes it hard to belive its mechanical.

Sounds electrical to me

I'm afraid so.

 

[chrisgarza]

Well no boost leaks, no compression issues, maf is ok, tps ok, have you checked fuel pressure yet? Check at the rail and see where its @ on idle and under load. If its shady grab some fittings and check before and after the filter.

 

[COdsm]

Well no boost leaks, no compression issues, maf is ok, tps ok, have you checked fuel pressure yet? Check at the rail and see where its @ on idle and under load. If its shady grab some fittings and check before and after the filter.

TPS is fine, because it hasn't had a negative affect on other performance. If the problem is fuel, my only guess is It's clogged injectors and by revving I'm "purging" them. That's my only guess that would cause the inconsistency.

 

[miguelmcv]

Have you checked your ICS?, Test it and see how it is, they can be a pain in the $$$.

 

[slo2spool]

Having access to a scan tool would do wonders for you but +1 on the ICS. If we all had a nickle for every DSM idle issue we would all have enough money to fix everything that caused DSM idling issues.

 

[COdsm]

ICS? I'm familiar with ISC being idle speed controller... Or are these one in the same, just different acronyms?

Having access to a scan tool would do wonders for you but +1 on the ICS. If we all had a nickle for every DSM idle issue we would all have enough money to fix everything that caused DSM idling issues.

:: That's why I had to ask, there are so many of them out there. The problem with a scan tool is I haven't figured out a way to recreate the problem.

 

[GSTurbo1]

ISC going bad?

 

[COdsm]

ISC going bad?

I'll take that as a yes hah