engine hesitation

[mercurygm88]

ok, just wondering. I will be interested in hearing how replacing your TFI module went and if it fixed the problem.

Well I fixed the silly thing I replaced the TFI and the dizzy at the same time and no longer have any missing/sputtering/jerking while cruising 65 so im not sure which one it was but it was one of the two.

[jpc]

OP: have you checked the computer for codes?

Your car might be new enough to illuminate the CEL when the computer isn't happy. Older cars don't.

[mercurygm88]

OP: have you checked the computer for codes?

Your car might be new enough to illuminate the CEL when the computer isn't happy. Older cars don't.

yeah check it for codes if you havent already the 88-91 cars will illuminated the CEL when unhappy 87 and older only does it for overheat or low oil pressure. Im almost positive these cars wont throw a misfire code though as the whole time I had my problem i got a code 11 which means the system passed and theres no problems I picked up a code reader from my local oreillys for $30

http://www.oreillyauto.com/site/c/detail/EQU1/3145.oap?ck=Search_N0664_EQU_EQU1_-1_2207&mn=Equus&mc=EQU&bn=Innova&bc=EQU1&pt=N0664&ppt=C0103

[MattDoscher]

Nice job fixing the problem! I know you're relieved to finally have it fixed and no longer have to worry about it. I'll have to keep the TFI and distributor in mind also when I look at mine next weekend.

[mercurygm88]

Nice job fixing the problem! I know you're relieved to finally have it fixed and no longer have to worry about it. I'll have to keep the TFI and distributor in mind also when I look at mine next weekend.

um actually scratch that I found out today I didnt fix it its still exactly the same and I really dont know what I can do about it now because everything is new the fuel pressure is about 37psi I have 180-190lbs of compression on all 8 cylinders and am lost as to what could be causing this problem. The only things I can do is to check my sparkplug gap and replace the plug wires even though there brand new ford racing wires. The 02 sensors, ambient air temp sensor, and coolant temp sender and sensor havent been replaced but I doubt theyd be able to cause this problem, and I doubt the 02's are bad because i still get 23-25mpg highway. So now what do I do.

[sly]

check fuel rail pressure... the pressure regulator... rule out fuel delivery issues. on a lopo, it should regulate the fuel rail somewhere between 30 and 40 PSI of fuel pressure vacuum removed from the regulator should cause higher psi. if the transition in pressure is slow... this could cause the hesitation too.

(I don't remember if this has been checked or not)

[mercurygm88]

check fuel rail pressure... the pressure regulator... rule out fuel delivery issues. on a lopo, it should regulate the fuel rail somewhere between 30 and 40 PSI of fuel pressure vacuum removed from the regulator should cause higher psi. if the transition in pressure is slow... this could cause the hesitation too.

(I don't remember if this has been checked or not)

Ok ill have to check that out ive kinda been suspecting the pressure regulator but havent checked it both with and w/o the vac line attached. Ill have to see how long it takes to change.

[sly]

it should change damn near instantly. If the pressure gauge moves slowly (or doesn't change) the regulator may be the issue.

[MattDoscher]

ok, so I was able to do some troubleshooting and here is what I found.
1) I disconnected the green line to the EGR valve and I did not experience any hesitation driving in OD at the speed I would have otherwise noticed the hesitation. I did notice the engine "pinged" more w/ that line disconnected during acceleration. As soon as I re-connected the green line to the EGR the hesitation came back.
2) I drove around in D w/ the EGR valve connected and didn't notice any hesitation. As soon as I went back to driving in OD I would notice the hesitation come back. (This is w/ the green line to the EGR valve connected.)
3) I disconnected my IAC valve and the idle speed remained constant; did not drop or flutter or anything. So I guess my throttle plate screw has been messed with. Should I even mess w/ the screw since I have no engine idle concerns? The only reason I can think of why I would adjust that screw is to bring my voltage reading on my TPS down from what I think is a high reading to around 1V.
So it seems like my hesitation problems could be EGR regulator related since driving w/ it disconnected there is no hesitation. What do you guys think?

[mercurygm88]

ok, so I was able to do some troubleshooting and here is what I found.
1) I disconnected the green line to the EGR valve and I did not experience any hesitation driving in OD at the speed I would have otherwise noticed the hesitation. I did notice the engine "pinged" more w/ that line disconnected during acceleration. As soon as I re-connected the green line to the EGR the hesitation came back.
2) I drove around in D w/ the EGR valve connected and didn't notice any hesitation. As soon as I went back to driving in OD I would notice the hesitation come back. (This is w/ the green line to the EGR valve connected.)
3) I disconnected my IAC valve and the idle speed remained constant; did not drop or flutter or anything. So I guess my throttle plate screw has been messed with. Should I even mess w/ the screw since I have no engine idle concerns? The only reason I can think of why I would adjust that screw is to bring my voltage reading on my TPS down from what I think is a high reading to around 1V.
So it seems like my hesitation problems could be EGR regulator related since driving w/ it disconnected there is no hesitation. What do you guys think?

that sounds to me like the egr regulator Ill have to check mine out again even though I replaced it theres always a chance I got a bad part. Because my hesitation did go away for about a day after I replaced it.

[gadget73]

sounds like the EGR regulator is sticky. Try pulling the lines from it and spraying some WD40 in the ports, and pull the cap off the top to shoot some down the tube that pokes up into the filter. If the filter has turned to dust, clear the remains out.

idle with the IAC unplugged should be in the ~500 rpm range, basically lower than it normally idles at, but not so low that it stalls. May be worth tinkering with, but keep track of how much you turn the screw so you can put it back in the event that something goes funny. Could be the IAC died years ago and the screw was tweaked to make up for it.

[MattDoscher]

If I install a new IAC would I have to adjust the throttle plate screw at all? Or would the ECU automatically learn that the IAC is working and adjust accordingly?

Anybody have a picture of the EGR regulator filter assembly Gadget73 is describing? Just wondering what it looks like.

[mercurygm88]

If I install a new IAC would I have to adjust the throttle plate screw at all? Or would the ECU automatically learn that the IAC is working and adjust accordingly?

Anybody have a picture of the EGR regulator filter assembly Gadget73 is describing? Just wondering what it looks like.

In theory you should not have to touch the throttle plate screw after installing a new IAC but if someone has tampered with it in the past I would guess your going to have to. I'll have to look at my service manual and get back to you with the proper way to do it unless someone else gets there b4 me. Also do not buy one from autozone I had one and it was dead right out of the box. Sorry I dont have a better pic but the egr solenoid is located right above these two solenoids on the passenger inner fender where the red arrow is pointing you can find it by following the green vacuum line from the egr valve.

[sly]

prodecure is posted over there: http://www.allfordmustangs.com/forum...dure-ford.html

PDF warning.

[MattDoscher]

So I was finally able to get down to SC to work on the GM some. My EGR regulator seems fine, I removed it from the engine and sprayed carb cleaner through both vacuum ports and through the top port that runs up the middle of the mesh filter under the cap, there does not seem to be any blockage as the carb cleaner that went in one port exitted out the opposite port. The mesh filter was not deteriorated at all. I shook the regulator around and could hear some rattling which I assumed means the valve inside is not stuck and is moving freely. I did this same procedure to the other 2 valve assemblies that hang on the back of the upper intake manifold and look exactly like the EGR one that hangs on the front on the upper intake manifold. I removed my upper intake manifold and replaced the MAP sensor vacuum line, this line was in good condition, only slight dry rot at the manifold connection. I did find a hole in the vacuum line that connects btwn the upper intake manifold and some solenoid that is mounted on the wheel well behind the battery. (Believe this is the purge solenoid for the charcoal canister). I replaced this length of vacuum line hoping this was my issue all along but it wasn't. The car continues to hesitate upon light acceleration and at part throttle maintaining speed. I removed my EGR valve and cleaned both ports on the upper intake manifold as well as shooting carb cleaner into the plunger assembly on the valve itself. The EGR valve moves freely. I throughly cleaned my throttle body again as well to no avail. I'm still experiencing the hesitation/bucking regardless of if I have A/C on or not or in or out of overdrive. It does not do this if I'm driving w/ cruise on. I don't know if I need to just replace the EGR regulator and those other 2 regulators to try and isolate the culprit or what. I sure thought that hole in the vacuum line I found was my problem. Any suggestions are welcomed.

Matt