Timing off by a tooth? Needs alot of timing to run at idle
Timing off by a tooth? Needs alot of timing to run at idle got a customers 69 camaro in today and went to fire it up today.
Engine is a rebulit ls1 by local no name shop that does not build ls engines much...
228 228 duration cam with 588 lift and 112 lsa. stock heads ls1 intake but has long tube headers
At first no fire at all. Turned out all 8 injectos were stuck. Fixed that and tried starting. It finally fired but could not idle below 1400 rpms. Ive tuned quite a bit of cars and knew what the base settings should be. Next I played with idle air flow and that did nothing. I then locked the timing and started raising it. It was at 22-24 degrees. I upped it to 36 degrees and it would finally idle. Sounded crappy but all cylinders are firing. Why will it only idle at 36 degrees to 40 degree...Once it could idle i had to change the idle airflow back to a decent range. This car doesnt want to even fire up with timing in the low 20's.
Engine is a rebulit ls1 by local no name shop that does not build ls engines much...
228 228 duration cam with 588 lift and 112 lsa. stock heads ls1 intake but has long tube headers
At first no fire at all. Turned out all 8 injectos were stuck. Fixed that and tried starting. It finally fired but could not idle below 1400 rpms. Ive tuned quite a bit of cars and knew what the base settings should be. Next I played with idle air flow and that did nothing. I then locked the timing and started raising it. It was at 22-24 degrees. I upped it to 36 degrees and it would finally idle. Sounded crappy but all cylinders are firing. Why will it only idle at 36 degrees to 40 degree...Once it could idle i had to change the idle airflow back to a decent range. This car doesnt want to even fire up with timing in the low 20's.
Playing with idle air in the tune will only work if the desired airflow is in the range of what the IAC motor can handle. If the IAC motor is dead or unplugged, it wont be able to do idle trims at all and could cause some really bad stuff like you are seeing.
Just a thought.
Other things to check for....maybe a vacuum leak. Could cause it to be so lean as to not run at lower RPM?
Throttle position sensor?
Being as its a swap into a vehicle that didn't have an LS stock, there is no telling how much of a wiring hack was done.
Just a thought.
Other things to check for....maybe a vacuum leak. Could cause it to be so lean as to not run at lower RPM?
Throttle position sensor?
Being as its a swap into a vehicle that didn't have an LS stock, there is no telling how much of a wiring hack was done.
The more I think about it, the more stuff pops into my head....
Does it have a MAF? or tuned for speed density? Does the TB have a hole drilled in it? Has the set screw been adjusted and/or the TPS reset?
Is there a wideband on it that will give you AFR? Hard to troubleshoot over the computer....LOL
Does it have a MAF? or tuned for speed density? Does the TB have a hole drilled in it? Has the set screw been adjusted and/or the TPS reset?
Is there a wideband on it that will give you AFR? Hard to troubleshoot over the computer....LOL
Is the TB set screw adjusted correctly to get you a tps voltage around .59? A 228 cam should idle ok off of the stock LS1 air flow tables. Might just need to add a bit of running air flow but nothing too crazy.
No maf. Tps is good. No 02s. We are just firing it up for a test run but this sucker doesnt even want to start. Ive done this on lots of engines and no issues with modified base settings. (similar engines ive done in the past tunes) Even when squirting fuel directly in the intake it wont want to start. That worry's me I have to lock the spark in the 30s to get it to fire and run. By shooting fuel in the intake it should light of instantly and idle for 5- 10 seconds. It will only do this with high timing.
Last edited by vannatta20; Apr 29, 2015 at 11:19 AM.
When cranking with a good base tune it hardly tries to fire. Plugs are wet when checked. Up the timing really high and then it will fire up. 36 degrees is way to high in my opinion.
Also it doesnt even try to idle at 900 with a base tune. It dies instantly below 1200 ish rpms. Bumping up the idle airflow did nothing to fix that. Maybe its fuel related pressure. Our pressure gauge is broke but the rail had lots off pressure when bleeding it. It needs to be checked. Fuel injectors where plugged and we cleaned them out with air pressure will shooting power to them to see the fuel pattern.
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36 degrees of timing is WAY too much timing for idle. I think you should pull your timing cover and verify the dots line up correctly.
Actually, tell you what. Do a compression test. With a 228 cam, you should be in the 200 psi cranking pressure range. If you are adding timing to get it to run, your cam would be retarded, not advanced, meaning your intake valve would be closing late, so your compression would be low. So, if you end up with 8 cylinders in the low to mid 100 psi range, that would be a strong indicator to check the cam timing.
Actually, tell you what. Do a compression test. With a 228 cam, you should be in the 200 psi cranking pressure range. If you are adding timing to get it to run, your cam would be retarded, not advanced, meaning your intake valve would be closing late, so your compression would be low. So, if you end up with 8 cylinders in the low to mid 100 psi range, that would be a strong indicator to check the cam timing.
Meh. I think it's somewhere else. Valve timing is different than ignition timing. I have my cam timing purposefully retarded and it idles at 22*. Cam timing mostly moves the power band around.
That's low. Typically, the next thing would be squirt some oil in and see if it improves. If it does, it usually means rings, and if not, it usually means valves. I'm assuming on a new build squirting oil won't make a difference.
If all 8 cylinders are in that range and oil didn't help, I would definitely pull the front cover, verify the timing marks, and take time to degree the cam. Another possibility that I've seen cause low pressure is if the pushrods are too long.
For reference, my trans am LS1 has a similar cam on the intake, about the same overlap, and my cranking pressure runs 200-210 on all 8.
If all 8 cylinders are in that range and oil didn't help, I would definitely pull the front cover, verify the timing marks, and take time to degree the cam. Another possibility that I've seen cause low pressure is if the pushrods are too long.
For reference, my trans am LS1 has a similar cam on the intake, about the same overlap, and my cranking pressure runs 200-210 on all 8.