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Back with engine issue--let's figure this out.


Tedybear

Well-Known Member
Firefighter
Joined
Aug 26, 2008
Messages
1,094
Vehicle Year
1994, 2001
Transmission
Automatic
My credo
Failing is easy. Everyone can do it.
Been a while, but this is the place that got my old girl back on the road in the first place!

The truck has been running decent (about 20 mpg actually) however the last few days? It's got me a bit rattled.

Hitting around cruse speed, 55-70 is when this acts up the most. And seems to be when it's under a slight-moderate load. (have not tried to power it out of this) The truck will run fine--and then it will just quickly cut out with a rapid power loss--we are talking like kicking the key on/off for a split second. At first I figured "Crap...transmission is acting up", then I stopped panic mode LOL.. Figured out if the transmission was slipping? The engine would surge "UP" and not "DOWN"....likewise, if the transmission was dropping gears back and forth? Hitting overdrive to 3rd then back? Would take a great increase in RPM when it does so.

This happens so quickly the tach does not have a chance to react. Going by the engine "sound". It just acts like it cuts out quickly and then cuts back in with a slight shudder (as if one hits the brake and then gas rapidly) as it goes back to normal 'load'.

2 years ago we did major work on the engine, new heads...full injector service/cleaning...Most sensors have been replaced/checked/etc.. It's almost like someone turned the key 'off' and then 'on' within a second while going down the road. It has not thrown a code, CEL is still off. (will pull codes in a day or two and see if anything kicks up when the heat wave breaks..not working on it while it's mid 90's outside with high humidity)

First thought was TFI dropping spark for a split second....It's a newer module (about 2 years old). Other ideas, fuel pump cutting off/on? Pickup coil in the disty?... Maybe the FPR acting up? Looking for ideas so I can kick out a large number of tests on Sunday (next day off) and hopefully get my daily driver back up and running without fear of it dieing on the highway.

The other items of interest? Slightly hard to start when engine hot and up to temp, it does start...but we have a gassy smell for a few seconds after it starts. Hard accel it appears to have a slight 'chuggle' which I first thought was transmission related--but these A4LD's when they start to slip in gear? Normally crap outright and never recover.

Just looking for ideas!

Regards--

S-
 
check all your wires for a short especially around the O-2 sensor wires maybe a loose connection or corroded ground pull the grounds apart and sand them check all the connectors and put them together with dielectric grease and make sure all the pins are pushed all the way in. I would run the codes and do the wiggle test ten seconds after the last code KOER press the pedal to the floor quick code reader still on and engine running an go around and wiggle tap all the connectors/sensors if there is a fault it will flash and store a code make sure you erase the memory first as not to get confused with old codes that may be stored, maybe clean the IAT or MAF and while your checking the wires disconnect the battery for 1/2 hour to reset the computer only if you change or clean a sensor.
 
On my 87 one day I decided to check/clean what wiring plug-ins I could get to on the drivers side fenderwell...so I checked and cleaned and then it wouldn't fire at all. The coil plug-in looked new inside....it was bad. A friend who does mobile diagnostics came over and hooked it to the computer jiggled the coil plug-in and it fired right up. He showed me on the readout how the graph was going up when he moved the plug-in. Might not be your problem but might be worth checking.
 
I hope codes pop up soon to help. Otherwise, it could be one of many things. Its probably all related...How is the IAC valve? Has it been cleaned at all? I would check the FPR too. These can both give it trouble starting.
 
I hope codes pop up soon to help. Otherwise, it could be one of many things. Its probably all related...How is the IAC valve? Has it been cleaned at all? I would check the FPR too. These can both give it trouble starting.

Thanks for the replies everyone. I'm weary of the FPR, it did pass the test before--but that was 2 years ago LOL. I've got a fuel pressure gauge set and a vacuum tester, so that's on my list for Sunday.

Hadn't considered the O2 sensor, but it's worth a check for the wiring and another ground wire check. The only thing recently we had to do (last month, may or may not be related) was install a different alternator. The old one had a bad bearing giving me a headache. Oddly enough? Found out someone modified the brackets and installed one out of a F150 truck. The salvage yard had a heck of a time nailing the right one down (it still had a recent rebuild tag, and it was fully checked right after we installed it. It's charging slightly higher then the old one used to-voltage wise--but never goes above 14.8vdc)

The IAC is new--within the last year, along with the TPS. (had a bad spot).. The ol' gal has been running fantastic for the last 10 months with the only issue being a coolant leak from a defective water outlet. (it never overheated--we kept a close watch on the coolant level until we changed it out)

I would be tempted to suspect bad gas, however it 'bucked' (for lack of a better word) a couple of times last week, and this week it really acted up on a different tank of fuel.

:dunno: After getting 20mpg out of her? Maybe it's her way of telling me she don't like extreme heat LOL! It's been pushing high 80's and mid 90's here for the last week.

Someone suggested, for the hard starting issue--the engine computer coolant sensor might be defective. Telling the system to dump in more gas then needed--starts to flood out--starts--and then smells like the poster child for Exxon.

If I had a longer hose for the fuel pressure gauge? I'd love to have it sitting on the hood while driving and keeping an eye on it. Kinda feel like a bad game of Russian Roulette with it. This might wind up being a problem that can't be fixed until it fails completely.

Thanks again for the ideas, keep 'em coming and I'll start working on it for the weekend.

S-
 
Updates:

This may or may not be the cause of the bucking. However it does explain the gassy smell after it's started...after sitting for about 20min to an hour.

Put the gauge on the valve to check the pump and FPR. Have 32lbs with full vacuum, and 40 with no vacuum. However I left the vacuum hose unhooked for a short while--and after about 5 minutes? Steady drips of fuel out the vacuum hose. This would make sense of the gassy hard to start problem...it's pre-loading the intake with raw fuel after sitting for a short while.

So the FPR is toasted, and I suspect this could also create the issue with the power problems. Sure it's running pressures up and down with vacuum, however I left the vacuum gauge on the hose at about 20inches of vacuum--zero fuel loss, and the pressure sitting 'off' didn't drop for several minutes.

Now would a break in the rubber seal possibly do this?: At lower power and high vacuum--it's in a position where it wouldn't leak by. However at lower vacuum (I have a driving vacuum gauge on my dash) Once the 'load' hits about 5" of vacuum during cruse speed going up a slight incline...that puts the rubber seal just at the right spot where it starts to seep fuel into the intake. Now that would create a 'rich' condition, and the computer would attempt to lean out the mixture....then once corrected? The cycle repeats again.

This is going to get replaced in any event---and I'm also planning on saying "Screw it" and pulling the entire disty out and replacing it with a rebuilt one complete with new TFI and pickup coil already replaced. (I'll scarf off the TFI from the old one before returning it for the core. Should make a good spare) I've been bitten before by the pickup coil in the disty failing with busted wiring in the past, and it's the factory one. (over 20 years in service).

Any ideas or feedback?

Also as a side bar note-- I did find at napa a replacement FPR that has a low cost of about $25 bucks. If the warranty is good, I'll probably give it a shot. That way I can cover the expense of the upper intake gasket and rebuilt disty at the same time.

S-
 
sidebar note: Passed the wiggle wiring test with flying colors. I also went to town tapping and flexing the connector(s) at the coil itself. Didn't even get a hic-cup out of it.

S-
 
If napa is selling a FPR for 25.00 you beter grab it, all the "other" parts stores around here want 90.00 to 110.00 for one.

I guess I betteer check with the local napa too, I just thought they where always higher then the rest.


Robert

p.s. I also am having the same problem you are, my 89 bronco II is hard to start when it's been sitting for awhile, and also having the quick on/off problem when driving, also when trying to pull out or accelarate it stutters all over it's self.
 
Well. If it's hard to start after sitting for a short while (overnights is not a problem, starts up within a few turns of the engine) And it smells like an Exxon factory when it does start? My money would be on either injectors leaking badly, or the FPR.

The injectors in mine do "Weep" slightly while under pressure and not running (did a key test with the injector rail hooked up but removed from the intake) We just kicked our key on/off to prime the pump/system. Each injector shows a slight weep from the needle valve. However it's so tiny it's never been a problem. We disassembled each injector and cleaned it with new fuel socks/micro filters. Only had two that refused to clean up.

I'll be picking up the FPR from NAPA tomorrow. The local warehouse had it in stock, so it's been on their shelf all day today waiting for the pick up at the local store.

S-
 
Update before I forget!!!

Napa's FPR for $28 bucks? Included all the parts (hose and clamps for the return line) and the truck nailed just over 20 mpg again. No more heavy gassy smell when I restart. (unless it does it's normal start/stall/restart.....I'm used to that, been doing it for 2 years LOL) heck, it's actually been decent the last couple of weeks.

Figured I'd let everyone know. It appears to be cured....(until the next part takes a dump on it)

S-
 
horah

I'm going to take the webpage ad of NAPAs ad for the fpr at $28 to O'Riellys and let them match the price :)




Robert
 
horah

I'm going to take the webpage ad of NAPAs ad for the fpr at $28 to O'Riellys and let them match the price :)




Robert

LOL. Good luck with that one. Napa lists 3, and due to being busted to the point of can collecting until payday? Had to use the cheap one. The main thing I did note? Warranty...Not that great on the cheap one...But it's doing the job and the truck is running decent. (or as decent as it can with how many miles is on it??? LOL)

S-
 
every time I go to O'Riellys to price something, they always say "If you can find it cheaper, we'll match it", so I'm going to try them out. :)

I'm living on 1200.00 a month, so I know about trying to save every little bit.


Robert
 
That's really interesting. I had a very similar problem happen with my truck for a while about a year ago, ended up being my TFI module. Never heard of a FPR going bad like that, hehe... nice catch though man, glad to see your problem already fixed =].
 

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