Running terrible, help
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Running terrible, help
I have an 88 f350 dump truck, 2 wheel drive with 351 and 5 speed and 93000 miles. I had valve cover and exhaust leaks to fix and it has not run great for some time. I replaced the manifold gaskets and built an exhaust, replaced vc and plenum gaskets. The egr tubes were rusty, so I cut them off and welded them closed, put bolts in the back of the heads and a plate between the valve and intake. I got it all back together and it runs terrible. Since then I have adjusted tps, cleaned throttle body, replaced iac, replaced o2 sensor, checked fuel pressure, changed fuel filter and regulator, double checked plugs which all look the same, searched and searched for vac leaks, made sure timing is at 10 degrees advance with spout out, and it still shakes at idle and has no power. I don't know what else to do. Any ideas?
Cargo Master
Joined: Mar 2010
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From: Laramie, WY
What was the fuel pressure? Does it increase when you unplug vacuum from the regulator?
When was the last tune up?
If you induce a vacuum leak (unplug brake booster line or something to that effect) does it stumble more (possibly stall)?
When was the last tune up?
If you induce a vacuum leak (unplug brake booster line or something to that effect) does it stumble more (possibly stall)?
Lead Driver
Joined: May 2011
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Did you pull codes?
You probably snapped a vac line or few when you did the work. Check vac lines, if you can't visually see a break, use a vacuum tester on the lines starting at the vacuum tree on the intake.
A patronizing question, so sorry, did you put all the vac lines back where they go? Egr, map, fpr?
You probably snapped a vac line or few when you did the work. Check vac lines, if you can't visually see a break, use a vacuum tester on the lines starting at the vacuum tree on the intake.
A patronizing question, so sorry, did you put all the vac lines back where they go? Egr, map, fpr?
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I believe I put all the necessary vac lines back in place. I do not have one to egr as it is blocked off. I did pull codes and got a 34 and 85. The egr isn't operating and the vent valve is gone. My understanding is that if the ecu detects a problem with egr it will remove it from all calculations. Is that correct?
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Double check plug wire routing and make sure 5 and 6 are well separated and there are no wires leaning on metal, change them if they don't look recent. If that checks out do a compression and leakdown test.
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Lead Driver
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Yea what he said above is what I was eluding to. You can block off the egr but you still need to have it hooked with electric and vacuum. Vacuum runs from the intake to the vacuum canister, canister to the egr solenoid, solenoid to the valve. Not having it hooked up can definitely cause running issues, but doesn't sound like your only one.
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The bolts broke off the canister and I didn't put it back. Do I need to put it back or can I just put vacuum direct to egr? Or am I better off to by one of those egr delete solenoid things on eBay? I will also do compression test soon, but wouldn't I see a difference in one of the plugs if I had a mechanical issue?
Cargo Master
Joined: Jun 2013
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From: Somewhere n North America
I have an 88 f350 dump truck, 2 wheel drive with 351 and 5 speed and 93000 miles. I had valve cover and exhaust leaks to fix and it has not run great for some time. I replaced the manifold gaskets and built an exhaust, replaced vc and plenum gaskets. The egr tubes were rusty, so I cut them off and welded them closed, put bolts in the back of the heads and a plate between the valve and intake. I got it all back together and it runs terrible. Since then I have adjusted tps, cleaned throttle body, replaced iac, replaced o2 sensor, checked fuel pressure, changed fuel filter and regulator, double checked plugs which all look the same, searched and searched for vac leaks, made sure timing is at 10 degrees advance with spout out, and it still shakes at idle and has no power. I don't know what else to do. Any ideas?
Explain the first 3 minutes of your current Cold Start-up? (First 30 sec? Next 30 sec? etc.)
Also, how does the current Cold Start-up compare to the old Cold Start-up?
Chasing potential vacuum leaks are tedious, there is the smoke test procedure, or check each line at a time, or cap/plug all lines (except MAP & Fuel Regulator, run temp new lines to these devices).
Do you have a Tachometer?
Last edited by vjsimone; Mar 3, 2017 at 09:59 AM. Reason: Adding text
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It ran bad before, but differently, has had a shake for a long time and would stay revved up to like 1500 for a few seconds after you touch the pedal. I just started it cold, it is below freezing. It started quick and idled high, then died after about 15 seconds 3 times without me touching the pedal, the 4th time it idled high for about 30 seconds, then idled down and stayed running with a little shake. Sounds good when free revved, but big lack of power, even compared to before when I drive it. It does idle up a little bit and smooth out if I disconnect vac to fpr and plug it. I tried disconnecting and plugging the other vac lines with no change. The only ones connected currently are MAP, FPR, Line to dash, PCV and brake booster.
Cargo Master
Joined: Jun 2013
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From: Somewhere n North America
I believe the critical sensors are the MAP, ECT, ACT, & TPS. You may have to test these to prove you don't have an issue with them.
They have reference voltages as well at the connectors and they should be verified.
You mention the TPS, is your signal at closed throttle adjusted to spec?
A good vacuum line to the MAP is important.
They have reference voltages as well at the connectors and they should be verified.
You mention the TPS, is your signal at closed throttle adjusted to spec?
A good vacuum line to the MAP is important.
Last edited by vjsimone; Mar 3, 2017 at 02:59 PM. Reason: Adding text
Lead Driver
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You can't run egr straight from the intake, it won't open properly and will likely throw a code. You could tap your brake booster and run a line from it to the egr if you didn't want to source another vac canister.
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So I rigged the egr back in to see if it made a difference. I ran vac to the elec solenoid, then from that direct to egr. Didn't change at all, but I did not have the canister. I will try to add the canister in also, or maybe just pick up one of those delete sensors. I just picked up a map sensor also. I tried disconnecting the vac from it and it didn't really change anything, so maybe it's worth a shot since I don't have a meter that reads Hz to test it. I did check the voltages there and they were fine.
Cargo Master
Joined: Jun 2013
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From: Somewhere n North America
You might try a new temp vacuum hose to the new MAP. Plug the old hose at the MAP end. Unplug the vacuum line going to your dash controls, and plug the new MAP hose there.
FYI - Sears has a multi-meter with Hz for under $25.
FYI - Sears has a multi-meter with Hz for under $25.
Last edited by vjsimone; Mar 3, 2017 at 03:02 PM. Reason: Adding text