Just got a 1990 Bronco, general advice and info on year?

[ErrorS]

I just picked up a 1990 Bronco in a trade.. it has a 351w and e40od.. just wondering if there's anything I should know about this particular year? has 3.55LS rearend which is nice.. suspension is saggy compared to my 1980s, but the frame and steering components are almost completely rust free, less rust than my 02' honda has honestly.. a bit of body rust though, and there is a ton of play in the steering. the person I bought it from spray painted it black and didnt bother covering the windows with tape, or finishing the hood. honestly, the 351w is lacking in power, I expected a bit more from a 90s EFI engine (the carb'd 400 in my 78 would smash it, with same torque and 40 less HP). changed a faulty TPS and codes I was getting before are gone. It's also idling at about 1500RPMs in park, it will spike to 2k at a stop then slow to 1500. Cleaned the IAC really well. It also has a leaky transmission, one of the bolts were stripped out. I tried putting a sae bolt in (one size above the metric, 5/16 maybe?) and it didn't hold. Is the tranny aluminum? I might need advice on how to tap this hole.

[greystreak92]

Those RPM's are high at idle. You most likely have a vacuum leak or two. The curb idle should be about 800-1000 and drop lower in gear. Check your timing as well with the engine warmed to normal operating temp. It should be 8-10* BTDC with the SPOUT connector removed. The Red Link in my signature gives more info as to where to find the SPOUT connector and what it does.

THe E4OD casing is indeed aluminum. Not all of the pan hardware will allow leaks as some of the holes for the bolts are not drilled all the way through the casing simply because it is thicker in some places above the pan. Those that DO allow leaks when the bolts are missing or stripped can be re-tapped one or two sizes bigger and not affect the ability to get the larger bolt through the hole in the pan in most cases.

Be aware that the E4OD was introduced in the truck line in about mid-88 to early 89. and they had issues. They were not as reliable nor as hearty as units built after 93. They don't like high torque situations (you can't keep a pre-93 unit intact behind a diesel for more than a couple years in my experience). Ford actually tossed the entire casing after the first production run (1989 model year) because of the inherent internal problems. This is why a first-run E4OD is usually discarded for a newer unit when it fails. If you ever have more problems than leaks and the unit needs rebuilding, it isn't an inexpensive job ($2500-$3000 typically). However, when it is redone, the ONLY parts available to rebuild are all of the post-93 components that helped its performance and longevity greatly so a rebuild will be worth the investment should it become necessary.

[ErrorS]

it seems alright otherwise, it shifts strong and sounds good.. ive been running it low on fluid, as has the guy who had it before me, so im not sure if it will last..

the bronco is in exceptional condition in regards to wear and tear, just homemade repairs and body work (if you can call it that) lower the value.

are there any vacuum diagrams so I can track down leaks? I found one, to some solenoid or something coming out of the firewall, had a small white plastic tube, but I can't imagine that alone was enough of a leak.

[ErrorS]

i found the diagram, there's one on this site and one under the hood of my truck.. it's actually pretty simple, in some ways less complicated than the older vehicles I have.

tracked down one and got the idle down to about 900 in drive, still high.. but i tried crimping hoses and it didnt drop at all, so it might be at the TB, intake, or another issue completely.

the vss wouldnt cause a high idle in park, would it?

[alxsnmr]

Before you go replacing parts, you already started on the vacuum line replacement which is usually recommended by myself if the original lines are factory plastic, go to fordfuelinjection.com to find out about the parts that the EFI system relies on. Also, acquire a DMM (digital multimeter) and use that to test the acceptance range of the ECT, ACT, TPS, etc. before you just replace these parts. It gets expensive fast changing these items out.

High idle is cause mainly by an uncontrolled/unaccounted for air by the computer getting into the motor. The next most frequent is either a faulty sensor(s) or actuators, and then a weak throttle return spring could cause this as well. Since you claim the motor is feeling week, it would be ideal time to do a full tune up to rule out bad plugs, wires, or mis advanced distributor.

[ErrorS]

ruled out throttle return spring (pushing on the throttle from under the hood doesnt lower idle) and the tps was definitely broken.

when I unplugged the IAC, there was no difference in the idle, does this give me clues as to what it is? also, there is a vacuum line that looks like it goes into a selenoid or switch or something in the firewall, when I unplug that the idle goes to a normal level, but surges up and down.

I just now found the PCV valve and im in trouble for spending so much time on it.. other than the PCV (which goes to manifold vacuum, correct?) , i think i ruled out all vacuum. PCV valve looks nasty from the outside, so maybe it's stuck open.

oh, the exhaust sounds like the truck may be running advance or lean, with that tad popping in it. I found it does it either too advance or too lean though, so im not sure which it is, and the engine is a tad noisy

[alxsnmr]

The PCV valve goes into the upper intake manifold and is accounted for Air. Maybe the best way for you to figure out if its a vacuum line is to disconnect and plug a line at a time until the idle becomes normal. If you block all the ports off including the intake and PCV, the engine should die, if not you have a manifold leak somewhere.

You said if you push the throttle against the stop it returns to normal idle?

[ErrorS]

no, it doesn't.. its just slow to return. I tried all of the lines from the T, unplugged it, blocked it and it didnt change the idle.

[ErrorS]

Ok, I found it.. it's the upper intake plenum. I was unplugging the MAP sensor because I had suspected it, the idle would drop.. but I realized that it was just causing it to run rich and dropping the idle, but it was also trying to pull more air which made the sound from the leak loud enough for me to trace it.

is the upper plenum hard to remove? It looks like there is a screw on the inside of it, the hardest part to reach. A screw? if it is, how in the heck am I suppose to remove it without stripping it?

by the way, thanks for your help everyone.

[ErrorS]

well, changed out the gasket and all is well... idles at about 750RPM in park.

also, gained quite a bit of power... drained the tranny and there was (for some reason) like 7 quarts in the pan? refilled it with about 3 and its showing up fine on the dipstick. No idea what that was about

[greystreak92]

The bolt between the front four and rear four runners in the upper plenum is indeed the most difficult one to remove. The rest is a piece of cake. Glad you got it fixed.

[ErrorS]

I got lucky, the screw came out with little issue once I found the right bit. For some reason all of the bolts were extremely loose, I could almost loosen them by hand. I think my gasket had just broken down that much.. when it came out, it was as hard as a rock and paper thin, just lifting the intake off made the gasket crumble into pieces.

[greystreak92]

Yeah the gasket needed replacing then. Time will vitrify a gasket like that but so does exposure to oil. Being as high up as that gasket is though. It would almost have to be excessive blow-by in the intake and you would know if that was the case. The truck would be showing signs of burning oil. I'd say it sounds like you just had a gasket go south on you and the replacement corrected the issue.

[ErrorS]

i do have a little bit of blowback, the engine has 211,000 miles on it though and most of the blowback comes from a cold start.. shouldnt be nearly enough to cause the intake leak.

actually, when I did the intake the PCV hose had come out. it had a 1/4'' thick layer of sludge throughout the hose, at some points it looked almost filled. I think the previous owner had gone a LONG time without an oil change and gunked up the PCV system at the least, probably causing a few other issues in the process (leaky rear main since I did my oil change). Ive never seen so much sludge in an engine in my life. Gonna do an oil change every 150 miles until I feel like it's as clean as I can get it.

even with the sludge, it runs remarkebly well. I've never been so impressed with a vehicle in my life considering age and make. This Bronco's problems are on-par (at worst) with the 97 CRV I just sold, and I considered that CRV the most reliable vehicle i've owned.

[greystreak92]

Welcome to the Bronco. I wouldn't part with mine for anything.

A lot of folks skip the PCV valve maintenance for one of two reasons. 1) getting to it is a PITA. 2) if you don't know where it is, FINDING it can be a challenge since it runs under and behind the upper intake plenum.