Ok, so we've got a 91 sunbird 2.0L (tbi) auto here that has 220k miles on it. Recently it's developed a detonation problem that I can't seem to figure out, plus I haven't had tons of time and I'd like to hear some ideas from people who might know a bit more about these cars than me so I can get it nailed down. Here is what I know:
It happens on acceleration pretty bad, worse under harder accel and will detonate at highway speed - if you stay off the gas and really baby it, it's less severe...
Also, this may or may not be related, but it idles poorly in park especially when cold, has died a couple times. It basically surges/hunts up and down.
I hooked up a fuel pressure regulator and it stays solid at I think 9 or 10 even when the detonation is occuring.
Plugs are white, no brown and are looking pretty lean.
I tried cleaning the injector and swapping another injector, no fix.
I hooked up a voltmeter to the o2 to see what it was up to and while surging in idle it will lean out, richen, back and forth from about .100 to .800
It's not throwing any codes.
New parts: map sensor, idle air control, coil, plugs, wires, cap, rotor, o2 sensor, fuel filter, newer gas tank
unrelated new parts: trans lines, radiator, alt, water pump, timing belt, starter & solenoid
I would think it would go lean if taking in unmetered air from say a big vac leak or intake gasket leak, but spraying some carb cleaner around didn't change engine speed and I can't hear anything either.
Any ideas? Things to test? Is it an ecu issue, or something mechanical? Thanks for any help!
• 86 Skyhawk wagon : 2.0SOHC swap, Megasquirt, 20SEH cam
• 93 Sunbird sedan : 2.0SOHC, Microsquirt, ported head, 10:1
• 88 Sunbird coupe : 2.0SOHC, turbo project car, giant tires
U may want to check ur egr valve.I am not sure what ur rides has but,if it has a vac line going to it,pull it off if the condition changes u need to replace it or remove it clean it and make sure the pintal inside it moves up and down freely.The egr can choke a eng cold or norm temp and really screw with the cars rpm's running in general.This is what came to mind right now and u may find this makes some or no diff but,worth checking bc most do not chk this and the carbon buildup inside this egr can cause havok like u decribed.Hope this helps.
I have checked the EGR, it does move freely up and down, I might have already tried disconnecting it, but I don't remember now. I'll try it again to see if it makes a difference. Appreciate the reply!
• 86 Skyhawk wagon : 2.0SOHC swap, Megasquirt, 20SEH cam
• 93 Sunbird sedan : 2.0SOHC, Microsquirt, ported head, 10:1
• 88 Sunbird coupe : 2.0SOHC, turbo project car, giant tires
Looking like it was the intake gasket, but that didn't help the surging idle. Better than detonation though...
• 86 Skyhawk wagon : 2.0SOHC swap, Megasquirt, 20SEH cam
• 93 Sunbird sedan : 2.0SOHC, Microsquirt, ported head, 10:1
• 88 Sunbird coupe : 2.0SOHC, turbo project car, giant tires
