I'm told this is a timing issue that Im having. But I need some more opinions. My 360 didnt do this. This is a 355 that I built. Getting the timing down to where the cam sounds like its supposed to there is no power. I had some detonation because of where the timing was at, so I put a colder plug in to eliminate that.

Is there something I could be overlooking? I just plugged the egr back in for the first time in 5 years. And I just took the chip out of the CPU and put it back to stock.

 

Sounds like you might have an air leak somewhere before your Throttle Body. Are you running a MAF system?

Check your snorkel for cracks or lose clamps?

 

It is MAF, I will have to take a look at the bottom side of the snorkel. It appears to be in great condition and everything is tight. Would a leak before the throttle body really cause this?

Oh and on the timing light it doesnt matter where the timing is as, it does this.

 

No expert here, just suggestions, and I'm not a mechanic, just a Rad guy.

Every car I've worked on with MAF surging has always been a crack in the ribbed snorkel. Air leaks in, ECM dumps fuel, O2 retards fuel..vicious cycle.

I only mentioned it 'cause it's something that may have 'just broke' during your swap.

Could be a leak @ your TB too.

 

Well the suggestions are appreciated no matter who they come from.

Im not a "mechanic" either but I have built plenty of engines in my life. And work on paying peoples cars all the time.

I will look into these suggested areas and report back tomorrow.

 

A leak in the intake anywhere after the MAF could cause a surge.
Also check all of your vacuum lines.

 

Headed to the shop now.

 

Small shots of Either around intake and vac lines while idling may help diagnose.

 

I don't think timing is your issue, but just for grins, be sure the bypass connector is hooked back up, it's on the pass. side firewall above the heater box, tan wire w/a black stripe. Remember that most surges are vacuum leak related. Remember that any leaks after the MAF is causing unmetered air to enter the engine that the ECM is seeing in the exhaust, which causes it to dump more fuel, which then makes it rich, which makes the ECM lean out the mixture. Are there any trouble codes?

 

Checked the grommet between the MAF and TB, looked good, no cracks, put it back on and on tight. Still does it.

Timing bypass is hooked up.

Car does not throw any codes.

 

Try disconnecting the IAC and see if the idle is stable. There should not be any vacuum to the EGR valve at low rpm's. The solenoid pulses around 2,000 and up.

 

Keep in mind that the ducting between the air cleaner and the throttle body is not the only potential vacuum leak spots. You could have one at any of the many vacuum lines that run around the engine, as well as where the intake bolts together. You could have leaks where the TB joins the plenum, the runners join the plenum, the runners join the intake, and the intake joins the engine. Heck you could even have a bad EGR gasket that's causing a leak, it can happen, but unlikely. Get you a can of carb and choke cleaner or WD-40 and spray it around the intake, if you see bubbles or the engine idle increases, then you have a gasket leak. Spray it around where the intake joins the engine (slowly) and watch there, if nothing happens, then move to where the TPI parts bolt together. Also remember, check all the vacuum lines.

 

not to steal thread... but mine does the same... but i have map...

on a 91... ideas?

same thing vac leak?

mine is ok on cold start.. warms up... gets warm.. idles about 600

then starts jumping like his... from 1000 to 4-500 .. sounsd like it gonna stall and goes back up to 1000... then keeps doing that for 30sec-1min.. then stops... for a bit.. then does again...

just curious.. could exhaust leak at or before o2 sensor caus?..

 

Thas exactly what mine is doing. It will level out for a little bit, and I think...

OH I GOT IT! but then it goes right back to it.

I'll trying spraying around the intake, and check the vac lines.

 

I have been having the same issues and recently found that 95% of my idle surging issues were related to a faulty IAC motor. Also i have read other posts on surging issues where you may need to adjust your MAF tables up or down depending on whether you are running rich or lean. However in saying that i have not totally fixed my idle issues yet and am also still learning what is the best way.