Help! Engine cuts out

[DeadRedex]

Hello all,

New member but frequently visit the forum for advice and such. But now I need serious help.

(Edit) if you know of a thread related to this please kindly share, I hate to be the guy that has posted this for the 100th time.

My problems are sub par MPG, rough idle at start and sometimes hesitant acceleration from a stop then slowly gain life. But the big one is while I'm driving the truck will suddenly drop to idle rpm and I will have to release the gas pedal then quickly press it down again to regain cruising rpm/speed happens in spurts of 3's. The sudden rpm drop happens 10 mins in to my commute, seems to be triggered by bumps in the road and only seems to happen when the outside temp is below 50 degrees. So far I have cleaned the IAC and replaced the: thermostat, coil pack, MAF, TPS, fuel filter, fuel pump, fuel pressure regulator, fuel pump relay, spark plugs (not the wires) the battery, EGR and a sensor I can't remember for the life of me near the egr on the intake manifold toward the firewall.

The most recent replacement being the fuel pump. Tested pressure with key on engine off which revealed that the pressure dropped to 28psi. It didn't act as poorly, mind you this is the first 30+ mile trek with the new pump tonight and it took a much longer time for the symptoms to occur which is a plus but it's still happening.

I'd love to hook it up to see what codes come up but a squirel set up residence recently and damaged some wires which I will fix soon. The CEL did at one time come on every so often but haven't seen it some on in months.

 

[trashtruck]

first thing I would do is shoot the squirrel. then I would make sure he hasn't set up home in the muffler or cat. then I would make sure all the wiring is still intact and hasn't been chewed.

 

[Rhett]

The CEL will be stored in memory, I'd pull the code(s) first

Could be a bad O2 sensor, since you've changed everything else.

Also, the camshaft synchronizer, if worn, can cause a problem in colder weather, but it is difficult to change and should only be done as a last resort. Pull the codes first.

 

[DeadRedex]

Pardon my ignorance, there are codes still being generated even though I don't see the CEL?

Side note, I'd love to shoot that little (insert expletive)

 

[Rhett]

Pardon my ignorance, there are codes still being generated even though I don't see the CEL?

No. (unless your CEL bulb is burned out) However, the ECU has keep alive memory (KAM) that is hopefully storing the CEL code you said you saw in the past.

I say hopefully, because you could have cleared the codes, but the only way to do that is to either jumper one of the diagnostic port wires or remove the battery for more than a few minutes time.

The stored code(s) might lead you in the right direction. As you probably know, most auto parts stores will read the stored codes for free. I don't want you to keep shotgunning it, changing parts with no resolution to the problem. That costs time and money and aggravation.

If you can't shoot the squirrel, get a varmint dog. I have a 22 lb. Jagdterrier that can catch those.

 

[DeadRedex]

Whelp, looks like I'll be repairing those wires so I can see what it might or might not have stored.

Today's commute too work was better, seemed peppy when I needed it to be, still rough idle, no cut out though. We'll see what she'll do on the way home this morning..... It's been cold out here in CO, so prime weather for the symptoms to occur....

Is there a time period that the computer will relearn and gradually improve?

 

[DeadRedex]

Drove it home and the rpm drop happened once which is an "improvement" but STILL idles rough and has a hesitant take off from a stop and intermittently during operation. Just feels laggy for lack of a better word.

 

[FR-425]

Ok. 5 bucks on the ECT.

 

[larrydd999]

I'd go with FR-425 - be sure you get the one that plugs in to the computer, not the one that drives the gauge. (No money, though...)

 

[DeadRedex]

Is it the same part? you kinda lost me at the computer not gauge bit.

 

[johnredcorn2170]

have you checked for a vacuum leak, i had an old f150 on cool or cold mornings it would have a really rough idle slow take off and die at red lights i took it to several mechanics and non of them could fix the problem, then one day my brake booster went out i changed it with a new one and boom there was a very noticable change for the better the rough idle went away better take offs and never died at a red light again

 

[larrydd999]

There are two engine coolant temperature senders, one for the gauge and one for the computer. The one for the gauge has only one connection (one wire), the one for the computer looks like the picture but sometimes the parts store gets them mixed up.

 

[2stroke]

This sounds more ignition related to me. I think the squirrels did more than you bargained for, and the giveaway to me is that you say it is triggered by bumps in the road.

 

[DeadRedex]

Ill definitely look into those things.

Don't know if it means anything but the idle is less rough when in park and the RPM's sit at 700rpm ~ but in drive at a stop it sits at 550-600~ and it idles rougher.

Also not sure the relevance but I found (heard) what seems to be an exhaust leak around the muffler area. A consistent puffing can be heard when near it at idle and accelerating by a concrete barrier or anything that sound can bounce off.

Thoughts?

 

[Rhett]

Thoughts?

Vac leak, ignition/starter/alt wires, ECT, O2 sensor.

But if a squirrel got loose under there, who knows what he chewed thru.

 

[DeadRedex]

I'll post pictures soon I reconnected one of the wires he chewed through and fixed a vacuum that went to the airbox. The wire I reconnected was a green wire that split off the cabling were you hook up the obd1 tester. It goes to a smaller connecter.

With that said it "seems" that I have a little more throttle response it could be placebo effect I'm not sure.