so i put a vacuum gauge on the car yesterday and it read 16 in of vacuum at idle.rev it quickly and all vacuum goes away keep it at 2000 and i get 21 in of vacuum then if you drop throttle vacuum goes up to about 24 in. i dunno if its bad valves or a vacuum leak. my step dad thinks its bad valves. :confused1:
vacuum leak or bad heads
- Thread starter Insayne
- Start date
rz5.0
Legend
Is it running like crap. Are you lean.
well i get slight detonation on 89 octane. the car has a miss at idle up to at least 2000 rpm. now im noticing a miss under heavy acceleration or should i say wot? any way i did a pull in first coming out of a corner and it was fine second had the miss. so just for grins i did another second gear pull and it happened again. i have an egr issue where when it gets good and hot the car stutters under cruise. so i have the valve un plugged and the line plugged untill i can find whats causing the stutter.
The vacuum @16 inHg is a little low depending on the cam. Here's a link to vacuum tuning.
http://autospeed.com/cms/title_Using-a-Vacuum-Gauge-for-Engine-Diagnostics/A_2393/article.html
What timing are you running? When was the last time you did a basic tune-up? Have you checked for DTC's? Too many unknowns to make an informed guess as the the source of the problem.
http://autospeed.com/cms/title_Using-a-Vacuum-Gauge-for-Engine-Diagnostics/A_2393/article.html
What timing are you running? When was the last time you did a basic tune-up? Have you checked for DTC's? Too many unknowns to make an informed guess as the the source of the problem.
factory cam. tune up last year new plugs a month or so ago. cap and rotor also a month or so ago. wires 4 months ago roughly. only codes are the egr code because the vacuum line is undone and capped and a sustained idle code due to an iac restricter plate.
it's lame.
rz5.0
Legend
What is your timing set to.
rz5.0
Legend
Have you done a compresion test.
extreme_21
New Member
Hey bud, I was having the same problems as you with the detonation and primarily when it was hot/warm..every sensor that I checked was perfectly in spec. I found my air pump leaking vacuum so I replaced it with the delete pulley from UPR, yet the fault was still there on being sluggish and detonating.
I vacuum tested the system and noticed on the EGR, with "slight" throttle on the road(under load) I would loose almost all vacuum**again only slight throttle**, which meant the EGR was open to early making the lean mixture.. On the FPR vacum was good at any throttle grade..looked at the vacuum circuit..FPR and EGR are on a different circuit, right away knew there was a leak on the EGR circuit side....btw: When I deleted the air pump I jammed bolts in the vacuum ends from the air pump..
So I capped off the throttle body and I smoke tested entire vacuum circuit..The bolts that I had jammed in the vacuum rubber fittings to the air pump where slightly leaking smoke, smoke was running along the threads to breath/vent..I removed the fitted and kept the bolts still in place, tried to vacuum the fitting with a pump, could not hold any vacuum...I removed the bolts and stuffed Right Stuff black silicone into the ports(let it dry)...Smoke tested again, no leaks, filled it with nitrogen from the smoke machine tester, system held the pressure..drove the car...AMAZING!! Instant fix!!...It's only been 1 day, but throttle response, detonation, sluggish, idle..has all been fixed..
Going to get a hold on a timing light and see if I can pull more that 10* now, compared to before I was at 8* to reduce the detonation..
If you can, I'd try and smoke test the circuit, even through the fittings are tight doesn't mean there not leaking..then use the nitrogen on the smoke machine to fill the system and see if it holds, if it doesn't..you'd be still shooting for a vacuum leak again..hope this helps dude
