Pennock's Fiero Forum
  Technical Discussion & Questions - Archive
  weird problems on a 2.8

T H I S   I S   A N   A R C H I V E D   T O P I C
  

Email This Page to Someone! | Printable Version


weird problems on a 2.8 by MordacP
Started on: 10-12-2007 01:51 PM
Replies: 15
Last post by: MordacP on 10-14-2007 10:18 PM
MordacP
Member
Posts: 1300
From: Clovis, California, US
Registered: Sep 2007


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-12-2007 01:51 PM Click Here to See the Profile for MordacPSend a Private Message to MordacPDirect Link to This Post
Since i put my motor back together it has been behaving abnormally. When I give it throttle, it revs up, then slows down, revs up and slows down, while i'm giving it the same throttle the whole time. Then sometimes it'll die shortly after I start it while it's idling, but i gave it a different IAC (not new, just different than the previous IAC) so that problem may be absolved.
IP: Logged
PFF
System Bot
Dodgerunner
Member
Posts: 9684
From: Lincoln, Nebraska
Registered: Sep 2004


Feedback score:    (61)
Leave feedback





Total ratings: 323
Rate this member

Report this Post10-12-2007 02:11 PM Click Here to See the Profile for DodgerunnerClick Here to visit Dodgerunner's HomePageSend a Private Message to DodgerunnerDirect Link to This Post
Questions.

You problem sounds like it might have vacuum leaks yet.


When it idles does it idle fast?
Have you verified fuel pressure?
Is your MAP sensor connected vac and electrical.
IP: Logged
MordacP
Member
Posts: 1300
From: Clovis, California, US
Registered: Sep 2007


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-12-2007 03:32 PM Click Here to See the Profile for MordacPSend a Private Message to MordacPDirect Link to This Post
MAP is all connected. On a cold start it idles at 1500 and then goes to 900, which is normal. I have no idea how to verify fuel pressure. I forgot to mention in my first post, there's is black junk coming out of the tailpipe. Here's a pic:



Is it possible that this is caused by too far advanced timing?

Something else I forgot to mention, it was fine last night. Idled good, smooth, reliable. The difference between last night and this morning is that I put the thermostat back in. I highly doubt the thermostat is causing this, but I like to keep an open mind.

[This message has been edited by MordacP (edited 10-12-2007).]

IP: Logged
CC Rider
Member
Posts: 2037
From: Cameron Park, Ca
Registered: May 2001


Feedback score:    (14)
Leave feedback





Total ratings: 61
Rate this member

Report this Post10-12-2007 04:03 PM Click Here to See the Profile for CC RiderSend a Private Message to CC RiderDirect Link to This Post
How long have you had it running once you got the motor back together?
Could the ECM be resetting itself after all the work you did?
Did you adjust the IAC before installing?
Any codes since the work being done?

What work did you do to the motor?

IP: Logged
MordacP
Member
Posts: 1300
From: Clovis, California, US
Registered: Sep 2007


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-12-2007 04:22 PM Click Here to See the Profile for MordacPSend a Private Message to MordacPDirect Link to This Post
How does one adjust the IAC and why? I changed the head gasket. I have been running it less than 24 hours. These spontaneous problems do make it seem like the computer is figuring stuff out. The service engine soon light isn't on. Or do i have to jump those two terminals in order to see codes?

What about the black stuff?
IP: Logged
MordacP
Member
Posts: 1300
From: Clovis, California, US
Registered: Sep 2007


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-12-2007 04:25 PM Click Here to See the Profile for MordacPSend a Private Message to MordacPDirect Link to This Post

MordacP

1300 posts
Member since Sep 2007
It would make sense to me that it's a fuel pressure problem. That black stuff could be unburned fuel, and the unresponsive throttle would also make sense. So, how do i check the fuel pressure?
IP: Logged
BobadooFunk
Member
Posts: 5436
From: Pittsburgh PA
Registered: Jun 2003


Feedback score: N/A
Leave feedback





Total ratings: 128
Rate this member

Report this Post10-12-2007 04:36 PM Click Here to See the Profile for BobadooFunkClick Here to visit BobadooFunk's HomePageSend a Private Message to BobadooFunkDirect Link to This Post
you need a fuel pressure gauge (harbor freight, $15) its called a "fuel injection pump tester"

itll look something like this


you connect it to the schrader valve (looks like something you would put air in on a tire)

i dunno what its supposed to read (i think mine may be low) but that how!
IP: Logged
Robert 2
Member
Posts: 2401
From: St Hubert Quebec Canada
Registered: Jan 2006


Feedback score: (4)
Leave feedback

Rate this member

Report this Post10-12-2007 05:54 PM Click Here to See the Profile for Robert 2Send a Private Message to Robert 2Direct Link to This Post
45 PSI key on not started
35 PSI running idle and could be 40 PSI at 60MPH
IP: Logged
Thegiz
Junior Member
Posts: 5
From: Forest Hill,MD,USA
Registered: Sep 2007


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-12-2007 07:45 PM Click Here to See the Profile for ThegizSend a Private Message to ThegizDirect Link to This Post
I would cheek the egr tube near the manifold and other vac, hoses
IP: Logged
Dodgerunner
Member
Posts: 9684
From: Lincoln, Nebraska
Registered: Sep 2004


Feedback score:    (61)
Leave feedback





Total ratings: 323
Rate this member

Report this Post10-12-2007 08:20 PM Click Here to See the Profile for DodgerunnerClick Here to visit Dodgerunner's HomePageSend a Private Message to DodgerunnerDirect Link to This Post
The black stuff is soot left from running rich normally. Then when you start up the water that forms in the exhaust from shor runs picks some of it up and spits it out when you start the car.

If you have bee running the engine without the stat it will run richer for longer since it does not heat up as fast.

As far as setting the IAC as long as it was not out very far when you installed it, (like an inch or less) you should be ok. Just as long as it was not out far enough to get smashed inthe the seat when you screwed it in. If you have not driven the car very much or not fast enough the iac has not set itself yet.

But it's a good idea to always check your fuel pressure first to eliminate that.
IP: Logged
MordacP
Member
Posts: 1300
From: Clovis, California, US
Registered: Sep 2007


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-14-2007 06:03 PM Click Here to See the Profile for MordacPSend a Private Message to MordacPDirect Link to This Post
I got a fuel pressure tester and performed the check. It went up to about 47-ish PSI when the igition was turned on and the pump ran, then QUICKLY (in a few seconds) dropped at least 10 PSI to 35-ish. The drop slowed down after that but continued to drop down to 10PSI. SI this normal behavior? I will give the results when I start the motor when my stupid battery (which is new and has died several times) is done charging. Good thing I have a warranty.
IP: Logged
PFF
System Bot
project34
Member
Posts: 2424
From: Menasha
Registered: Jan 2007


Feedback score: (1)
Leave feedback

Rate this member

Report this Post10-14-2007 06:37 PM Click Here to See the Profile for project34Send a Private Message to project34Direct Link to This Post
The 10 PSI you report is much lower than is typical with fuel injection, and in fact only a few PSI higher than what you'd expect with a carbureted system.
IP: Logged
MordacP
Member
Posts: 1300
From: Clovis, California, US
Registered: Sep 2007


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-14-2007 08:09 PM Click Here to See the Profile for MordacPSend a Private Message to MordacPDirect Link to This Post
Yeah, but that was after the pump stopped running. So it might be okay. I have also got a compression checker, so if anyone following this thread will tell what the compression is supposed to be after so many seconds of cranking, that would be swell. I looked in the haynes manual, and couldn't find it.
IP: Logged
Dodgerunner
Member
Posts: 9684
From: Lincoln, Nebraska
Registered: Sep 2004


Feedback score:    (61)
Leave feedback





Total ratings: 323
Rate this member

Report this Post10-14-2007 08:22 PM Click Here to See the Profile for DodgerunnerClick Here to visit Dodgerunner's HomePageSend a Private Message to DodgerunnerDirect Link to This Post
How fast does it drop down to 10 after cycling the key.
The 47 is a little high but could just be the gauge.
35-40 is more of a normal range.

However when you turn off the pump the pressure should sit in the 35-40 range for a while or drop very slowly.

If it drops to 10 in five min. then you have some leakage somewhere be that pump, reg. or leaking inj's...

IP: Logged
MordacP
Member
Posts: 1300
From: Clovis, California, US
Registered: Sep 2007


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-14-2007 08:32 PM Click Here to See the Profile for MordacPSend a Private Message to MordacPDirect Link to This Post
The strange thing about this fuel pump test is that i ran the pump a few more times, and the pressure kept within the range you mentioned. The pressure only fell the very first time I turned the key.

I cranked my motor for 5 seconds (counting 1-one-thousand, two-one-thousand.......) and the compression tester reads 140 lbs. Is this normal?

I also found a severed spark plug wire, this may be the cause of my woes.
IP: Logged
MordacP
Member
Posts: 1300
From: Clovis, California, US
Registered: Sep 2007


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-14-2007 10:18 PM Click Here to See the Profile for MordacPSend a Private Message to MordacPDirect Link to This Post

MordacP

1300 posts
Member since Sep 2007
I just started it and all is well. for now.
IP: Logged



All times are ET (US)

T H I S   I S   A N   A R C H I V E D   T O P I C
  

Contact Us | Back To Main Page

Advertizing on PFF | Fiero Parts Vendors
PFF Merchandise | Fiero Gallery | Ogre's Cave
Real-Time Chat | Fiero Related Auctions on eBay



Copyright (c) 1999, C. Pennock