91 Sport Poor Running; Help Diagnosing!

[Iceking007]

Hello it's been a while since I've posted here but I stop in from time to time and see what's going on and post a tidbit of help here and there....

However this time I need some info.

Over the 2009 Fall winter season my X has been acting up; all started with horrible to worse fuel consumption problems (actually dating back a year or two at the most earlier for long haul hi-way trips once ran out of fuel) But it got to the point that I was using 1/4 of a tank of fuel to get to work just 65kms from my house ALL Hi-way!

Then one morning (I work nights currently) I was leaving work and she wouldn't start as I was almost empty on gas wouldn't start even getting boosted and a 20L Jerry can in there however it sat in the shop for a few hours and new plugs, checked compression and lead down (even cold was VG!) and she started back up no problem.

This problem continued however the colder the worse it got as it warmed up or sat inside to start it ran better but not GOOD.

So over the coarse of the winter I have replaced this:
(in approx order)

-Plugs
-Cleaned K&N
-Fuel Pump/ Filter (got a reading of less than 15psi on the orig)
-MAF
-O2
-Injectors
-Pushrods
-Rockers
(now she's quiet and runs nice... under the circumstances)
-Temp sensor
-Rad
-Hi flow fan
-Coolant
-Two oil changes and flushes (lots of sludge found when doing rods n rockers)
-Cold air intake sensor
-PCV

I think that is basically it I have a record of everything I've done on the truck ever but this is just from mem... basically all sensors and things to do with the running plus:

Over the past few years I have done:
(in no order)

-Lifters
-Full head gasket intake gasket & bolts kit
-Spark plug wires (bosh premium / I believe)
-New Deep cycle bat
-Idle control valve
-Oil pressure switch
and other maintenance items ect.

Basically now I am experiencing these issues:

-Won't idle any longer than a few minutes
-Poor throttle response (it has gotten better before it would not accelerate above 3000 RPM and sometimes barely do 80KM/h on the HWY plus under full load acceleration it would stutter through the band and sit at 3000 now I can accelerate up to 4000 don't want to push it much past currently; and the band is smoother but not full power)
-Bad fuel eco even though it is improving I am getting 300Kms per 60L and twice now got 400kms thats about 16L/100Km but I used to get 500K on the hiway per tank on avg.
-If stalled while idling ie sitting at a light, it is hard starting it will turn over and over and over doesn't matter what throttle position it just won't catch. Sometimes it has to sit a few minutes then it will start but I try to rev it up and keep it from stalling while idling.

I think that is basically it; I did read on hear one member had at the very basic level similar symptoms as I and changed a few things like I did ie MAF and O2 (but his post was really short) he was looking for the EGR as I was just doing 5 min ago but apparently we don't have one, he changed the Fuel Pressure Regulator and his runs beautifully now.

I will order one of these on monday and see if there is any change but other than that every thing else IS BRAND NEW and I have atleast two Licensed mechanics working on this not to mention I'm a second year apprentice and going to school soon.

I appreciate any help regarding this! thank you!

Oh also the only other thing either related or not....

My truck seems to eat coolant I just did new rad and no visible leaks and it doesn't burn oil just drips from the pan but level will stay constant for months until I change. But coolant will only last maybe a couple weeks before I notice it's dropped or less.... but all the gaskets are newly changed so I don't understand this one!

 

[MrShorty]

One of the first things I like to do, even if the CEL isn't on, is to pull any codes from the computer.

You talk about replacing the FPR, but you don't mention ever having checked the fuel pressure. I would likely put a fuel pressure gauge on it and see what it is doing.

When you changed the spark plugs, what did the old ones look like? Some say you can tell a lot about what's going on inside an engine by the condition of the plugs. Were they fouled? If so, what did the deposits look like?

 

[Iceking007]

Yes I apologize, I had lots of info but left some things out.

I did do a fuel pressure test when I replaced the pump when I was first having these major issues, I got really low pressure readings off the rail but the new pump performed as it should I think in the 40psi range (can't remember the numbers now maybe around 20 but they were good and the stock pump was way low)

Also I have constantly been checking and clearing codes one that comes up this entire time (that I have been paying attention, have not logged these as sometimes they are frivolous) is Lean Bank 1 Ego not switching can't remember the number that lead me to change the MAF and O2 but no change still coming up as of yesterday.

Also got at PIP fault code.... but we didn't know what this one was, after a google search it said some things that were interesting:

1- Something about making sure CB radios are grounded and powered correctly ect... this is odd due to the fact that I used to have a CB and VHF in my truck (everything worked perfectly and back when my truck ran nice) but have since removed them and sold one... just a weird coincidence

2- Said something about faulty connection or bad readings from O2 sensors check connectors ect... this is odd b/c I noticed when I changed the sensor it had appeared as though there was a bad connection on one of the wires (one of the blk of the four wire system) as it appeared to be pulled out or not properly secure in the connector I pushed it in and kinda passed it off as nothing but I should go back and double check this as I did get an error stating a relevance.

Ah and lastly yes spark plugs and innitial issue:

When I first changed and removed the plugs they were soiled heavily indicating Rich... which is weird due to the fact that the computer is reporting Lean...... a perpetual cycle lol

This ^ went hand in hand with my Fuel usage issue and the cold starting being too rich, I had black dust out the tail pipe of my truck and you could tell every single place I parked and started like a bred crumb trail.

This has since subsided but I think is still there to a minor degree tough to say especially since the weather is getting warmer out.

I believe I've checked the plugs since and they look not bad possibly a little fouled or rich (which I believe is still the problem) but can't recall exactly.

Hope that helps, thank you... if any more I will update!

 

[Vargas]

Bad O2 sensor making engine run rich results in poor fuel economy and dirty plugs. You've replaced the O2 sensor and the plugs, but perhaps the catalytic converter is clogged up from running so rich for so long?

 

[Iceking007]

Bad O2 sensor making engine run rich results in poor fuel economy and dirty plugs. You've replaced the O2 sensor and the plugs, but perhaps the catalytic converter is clogged up from running so rich for so long?

I understand what you are saying clogging up the system isn't good IE stuffing a rag in your exhaust (or classic banana) or a plugged drain at home.

However I would imagine this would affect more the overall running performance which I maybe used to have more; however now it seems to slight have gotten better?!

If this is the case however I am looking at doing an exhaust system any ways possibly this summer; if I have the cash for headers, and just getting rid of the whole CAT all-together like one my car and just putting in pipes and good muffler. Unfortunately I will have to wait for results to that

 

[Vargas]

A partially clogged cat will give a host of problems.

 

[MrShorty]

When diagnosing trouble codes (like a lean code) remember that codes point to problems in circuits, of which the sensor is only part. If replacing the O2/MAF sensor didn't fix the lean codes, then I'd be sure to inspect the wiring. You already mentioned a potential problem with the O2 sensor connector, you might take the time to verify that it is ok or not.

PIP (profile ignition pickup) signal is generated by the CKP (Crankshaft Position) sensor. CKP is a Hall effect sensor that sends a signal to the ICM. The ICM processes this signal (in conjunction with the PCM) to know when to fire the spark plugs. If you are consistently getting PIP codes, and those "unusual" causes don't seem to be part of the problem, I'd check the CKP/ICM circuits to make sure everything looks right.