maveRick
07-16-2004, 11:11 AM
Hey Guys,
I'm trying to get my '89 Mustang 5.0 to idle correctly. It surges from a very rough idle to a smooth idle - seemingly without reason. The engine is very sluggish when accelerating from poor (low) idle, and very responsive when NOT idling poorly.
Background:
1) I recently swapped motors. There was no problem with the idle on the original motor, only with the replacement motor.
2) I installed a 'B' cam on the replacement motor prior to installation. Note: This cam did not make another engine I had idle THIS poorly.
3) I am using a 160 deg Tstat. (note: before jumping to a conclusion on this, the idle has little or no change, hot or cold).
4) I removed the smog pump during engine swap (and plugged the vacuum lines).
5) I've 'screwed' with the idle screw - makes no difference.
6) I've polished all the grounds and re-tightened.
7) I've ensured all the electrical plugs are engaged tightly.
8) I've swaped the coil out with an MSD coil - seemed to help throttle response a little but has not affected the idle (much).
9) I've swapped the stock distributor with an MSD. Same result as 8.
10) I've adjusted the fuel pressure up and down to no avail (from ~37psi to ~42psi with line plumbed to FPR, higher when removed).
11) I removed the upper (Cobra) intake, replaced the gasket, and ensured the vacuum lines are terminated. There are three lines coming from underneath the upper (rest are plugged);
a) (1) ~3/8" line to vacuum manifold on firewall
b) (1) ~1/8" line going to vacuum 'junction' (for lack of a better word) on the passenger side
c) (1) ~1/8" dia going to FPR.
12) I've changed out the IAC with another one known-as-good. No change.
13) NOTICEABLE: THE EGR VALVE'S OPENING AND CLOSING IS COINCIDENT WITH THE IDLE'S FLUCTUATION.
a) When I remove the vacuum line from the EGR and plug the ends off (at EGR valve and hose), the idle rpm increases significantly and the throttle response is MUCH improved.
b) The vacuum reads ~10 in hsig (at idle) when the EGRV is by-passed and 0 when in hooked up (measured at firewall manifold).
c) When the EGR diaphram is 'engaged' (flexed towards rear of car) is when the engine's idle is at it worst. Best idle when diaphram is 'flexed' towards front of car.
I don't think the EGR valve is bad as it flucuatates with the vacuum change. I believe it to be something else (EEC?) causing the change in vacuum.
Also a question: Since I don't have another EGR valve (handy). Should I simply run it without the EGR valve hooked up? It seems to do the trick. What would be the harm?
Whatcha think?
Perplexed, I am
Rick
I'm trying to get my '89 Mustang 5.0 to idle correctly. It surges from a very rough idle to a smooth idle - seemingly without reason. The engine is very sluggish when accelerating from poor (low) idle, and very responsive when NOT idling poorly.
Background:
1) I recently swapped motors. There was no problem with the idle on the original motor, only with the replacement motor.
2) I installed a 'B' cam on the replacement motor prior to installation. Note: This cam did not make another engine I had idle THIS poorly.
3) I am using a 160 deg Tstat. (note: before jumping to a conclusion on this, the idle has little or no change, hot or cold).
4) I removed the smog pump during engine swap (and plugged the vacuum lines).
5) I've 'screwed' with the idle screw - makes no difference.
6) I've polished all the grounds and re-tightened.
7) I've ensured all the electrical plugs are engaged tightly.
8) I've swaped the coil out with an MSD coil - seemed to help throttle response a little but has not affected the idle (much).
9) I've swapped the stock distributor with an MSD. Same result as 8.
10) I've adjusted the fuel pressure up and down to no avail (from ~37psi to ~42psi with line plumbed to FPR, higher when removed).
11) I removed the upper (Cobra) intake, replaced the gasket, and ensured the vacuum lines are terminated. There are three lines coming from underneath the upper (rest are plugged);
a) (1) ~3/8" line to vacuum manifold on firewall
b) (1) ~1/8" line going to vacuum 'junction' (for lack of a better word) on the passenger side
c) (1) ~1/8" dia going to FPR.
12) I've changed out the IAC with another one known-as-good. No change.
13) NOTICEABLE: THE EGR VALVE'S OPENING AND CLOSING IS COINCIDENT WITH THE IDLE'S FLUCTUATION.
a) When I remove the vacuum line from the EGR and plug the ends off (at EGR valve and hose), the idle rpm increases significantly and the throttle response is MUCH improved.
b) The vacuum reads ~10 in hsig (at idle) when the EGRV is by-passed and 0 when in hooked up (measured at firewall manifold).
c) When the EGR diaphram is 'engaged' (flexed towards rear of car) is when the engine's idle is at it worst. Best idle when diaphram is 'flexed' towards front of car.
I don't think the EGR valve is bad as it flucuatates with the vacuum change. I believe it to be something else (EEC?) causing the change in vacuum.
Also a question: Since I don't have another EGR valve (handy). Should I simply run it without the EGR valve hooked up? It seems to do the trick. What would be the harm?
Whatcha think?
Perplexed, I am
Rick