Aftermarket Cam idle woes

jetski247 said:
lets say you unplug the o2 sensor, does the computer still use a base map to keep everything running?
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On a stock vehicle, this works pretty well. Everything is close to factory. On a modified vehicle, the Volumetric Efficiencies are all over the place, and on a Speed Density vehicle with no O2 sensor, the computer is totally blind. It works solely off of RPM, temperature and the default tables.
oilwell1415 said:
I get codes for my O2 sensor and PIP sensor all the time. No driveability issues at all, just the CEL and it usually goes off a few miles later. People have been spoiled by OBDII and don't remember how bad OBDI engine management systems are.
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No kidding! When the light came on Tuesday morning, I kind of stared at it dumbly for a moment, and thought, "Well, if it's there later, I guess I'll pull the flash codes..." In my car, I would've plugged in the Bluetooth OBD2 module, fired up Torque on my phone, and known exactly what the problem was. While sitting at a stoplight.
 
well it acted up again the last couple of days when the temp dipped into the 50's in the morning, while idling in the driveway. i usually start the truck and let it warm up in the driveway while the kids are getting ready, and i herd it drop down in rpm and was barely idling, the exhaust smells very lean and has a very distinct smell to it like other vehicles i own when they run lean.

as usual, it did this for about 5 minutes, the rpm returned to normal, and truck was fine, no cel. i do get a cel if i run the truck for about 15-20 miles but goes away if I turn it off, i haven't checked that yet. i lost my code reader and now have to jump the pigtail to pull the codes and watch the check engine light and just haven't done it.

so, what would make it start fine, after about 5 minutes, run lean as heck, then return to normal with no check engine light? well i would guess that a weak fuel pump would not be throwing codes and would make it run lean but this is the 3rd fuel pump assembly since this write up began. so either ive put 3 crappy fuel pumps in or its not the fuel pump, fuel filters were replaced when pumps were replaced, fuel pump fuse and relay have been checked, and relay was swapped out for another just incase. so without hooking a fuel gauge up and waiting for it to act up and see if fuel pressure drops, which leads to another question, say rpm drops, so does idle voltage, if voltage drops, fuel pump pressure drops too, even though its fine, it doesn't have proper voltage to work properly correct?
 
Voltage would have to drop pretty low for fuel pressure to drop. That's a guess since there's no data. You really need a scan tool to be datalogging to see what's going on. To me this sounds like what the speed density trucks would do when we tried to tune them back in the day. They'd run OK in open loop then going in to closed and run like crap, drop out of closed loop, then back in over and over. When I had my business I sold a scanner made by EASE that would datalog OBD-I stuff and it helped tremendously. Anyway without data, you will continue to guess and so will anyone else.
 
Could be an anomaly in the CTS or ACT sensor. As Ray said and I said before, you need to get a scanner on it so you can watch what's happening with the sensors when you are having the problem.
 
yeah, i know i know.........

whilst i wait for my scanner, ill start by monitoring fuel pressure to see what happens, i'll be monitoring voltage at the same time to see what/if voltage drops to and fuel pressure if effected at all. problem is, even with the scanner, its a hit or miss and a waiting game, by the time i get the scanner, temps will no longer be in the 50's in the morning.

what i guess i was asking is, what all would make it run lean enough to die besides the obvious fuel pump/fuel filter?
would a map sensor act up and cause it to run lean and not throw a cel?
would an o2 sensor act up and cause it to to run lean and not throw a cel?

and when i get this scan tool, does it show live data for several sensors at one time?

and after i ordered the mt2500, i realized i also need some special adapter to hook up to obd1 and personality keys too?

and what about this bosch?
www.ebay.com

BOSCH OBD1 & OBD2 AUTO SCANNER KIT Code Reader Tool GM Ford Chrysler Toyota | eBay

ABS and Airbag codes and definitions for most 1996-2015 GM, Ford, Chrysler, Toyota, Honda, Nissan, and Hyundai vehicles. Includes: 3.5" color display; OBD II, 6' extension, & cigarette lighter cables; OBD I cables: GM ALDL, Ford MCU/EEC-IV, Chrysler SCI, Toyota round & rectangular; trilingual...
www.ebay.com
 
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You're assuming it's lean :) At any rate if it's in open loop there's no feedback from the O2 and generally no code (at least as far as A/F is concerned). I know a lot of you guys are sharp enough to dial in A/F by smell (not being sarcastic), but I HATE ASSuming and refuse to do so. So I never factor in smell...
 
a lot of the watercraft and land vehicles i work on that are carbed and tuned by nose and rpm to set target a/f ratios but yes, its a guess and years of experience lol.....
 
If a carb is rich or lean, it's a simple matter of giving the fuel a smaller or bigger hole to flow through to correct the issue. A carb doesn't have half a dozen electronic sensors feeding data to a computer which then does calculations and sends signals to a dozen electronic widgets to make the engine run, and an issue with any of the sensors or widgets can cause a running problem that you can't identify just by looking at it.

I suggest the MT2500 because it's what I've used for over 20 years, it works, and it's cheap to buy. But it does have it's limitations due to being discontinued over a decade ago. If someone was starting from scratch that Bosch unit looks pretty good. There's something to be said for getting a new tool instead of a used one, and at this point all of the MT2500s are used.
 
i know how the two differ and work, i was referring to the smell it emits when its acting up.........it smells lean according to my nose, which is used almost on a daily basis to "tune" carbed vehicles.

so like the game of sudoku, if i apply my tools to this vehicle while its acting up while waiting on my scanner, it can help me in the right direction to find out what is wrong. and no, its not going to pinpoint anything but........i know its lean without a doubt, and giving it throttle also, veryfiys that its lean because sometimes, i can go wide open with the pedel and it remains at idle and sits there and pops very slightly through the intake manifold, sometimes will die instantly. which rich would bogg and smell rich as $#!* which it did with the custom ground cam with a budd load of overlap.

and the bosch, looks to need an adapter for the obd1 ford, which i think is yellow but i don't know anyone who has used one with any experience.
if it works like the snap on and is new and analyzes things, its an alternative.
 
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the bosch says it only graphs 96 and newer, so no obd1 graphs.
im learning the snap on mt2500 needs the ford primary cartridge as well as the 1a to read my 95, or so im told by the guy whos selling his on ebay.

and i forgot...................this computer has not had the capacitors replaced................what if that is what is causing the strange issues all this time....lol....
 
I would pull it out and check it. Take pics and post them. I’ve been wondering if that is your problem too.


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this is after i used a toothbrush near what looked like some corrosion, there was a tiny amount of white powder on the solder on the capacitor.
 
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Definite a couple of dead capacitors. They've leaked their guts. But man that computer is waaaaaay healthier than the one in my '94 was!
 
i keep the computer seams wrapped in heavy foil tape for roofing, since this goes to the beach a lot to help keep salt and sand out, i guess it worked pretty good.

well i'll send it off cuz my soldering skills on circuit boards suck. 100 is what they charged to do my a9p. anybody need an a9p?
 
while i shipped my jog1 off to get repaired, i installed my a9p and maf system since all my plugs/wires are still there, to see if it still did that strange cold start barely idle thing, which it hasn't yet. purrs like a kitten, check engine light comes on after about 10 miles which is egr related which the old ecm did.

so, im hoping it was the capacitor issue cuz this maf system runs this set up with less power. im lean, im deto'in at wot with this setup and power has fallen off compared to the speed density.

so i can richen it up with this stupid air adjuster which fools the maf signal to the ecm or swictc back to speed density. prob speed density.

does anyone know what the capacitors actually do? or control?
 
jetski247 said:
while i shipped my jog1 off to get repaired, i installed my a9p and maf system since all my plugs/wires are still there, to see if it still did that strange cold start barely idle thing, which it hasn't yet. purrs like a kitten, check engine light comes on after about 10 miles which is egr related which the old ecm did.

so, im hoping it was the capacitor issue cuz this maf system runs this set up with less power. im lean, im deto'in at wot with this setup and power has fallen off compared to the speed density.

so i can richen it up with this stupid air adjuster which fools the maf signal to the ecm or swictc back to speed density. prob speed density.

does anyone know what the capacitors actually do? or control?
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I cant remember off hand what they do specifically but I know my 93 was a random no start when I bought it due to bad caps. At least 1 or a combination of the caps controls fuel pump. I had the notorious key on no fuel pump prime. Jiggle the pcm and it comes right back till you hit a bump in the road. Replaced the caps and drove it 15k miles like that until I installed the new motor. I imagine they control more though because when it did run it would have a hanging idle or rough idle sporadically. But at the end of the day all these PCMs at best are 25 years old and a 30 plus year old design. They were limited in their day and are much more problematic now with age.

That said. Fuel content might be an issue with yours. They have drastically increased the ethanol content of modern fuels. Especially in the last 6 months with the shortages. Most of your modern systems can handle this by comparing knock sensors O2 sensors etc to make an educated guess on correcting the fuel tables. I really doubt these PCMs are smart enough to compensate for this. They definitely don't get near enough data to even try to make these corrections compared to a more modern system. I hate to say it but I think an aftermarket system may be your better bet to make it work properly. I really liked my PimpX. It idled flawlessly with the bigger cam. Like you I was borderline on the cam specs.

One final though. Have you verified the cam profile that they ground is actually the one listed on the card? Sounds crazy but they way QC and everything is going these days I wouldn't be surprised if it was off. Maybe one or 2 lobes being different could explain your issues. Especially since it doesn't do it on any of your "known good" camshafts.

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i never degreed the cam to verify the cam card. i just know it would not run that cam with maf or speed density. i then rebuilt the maf ecm and it still had the same problem. i put the five o cam in and it had zero issues and ran good with maf or speed density.

the speed density jog1 actually runs the system very well, with no noticeable deto at all, but im waiting for that to get back and therefor selling the maf kit/system in the classifieds.

what was going on was exactly what yours did, fuel pressure would just fall off randomly, and was intermittent. id watch fuel pressure drop, and kept replacing fuel pumps and relays for them to do the same thing, which was (or at least i hope) was the ecm all this time. i was blaming cheap china parts only lasting a couple days, then crapping out. the maf system has no issues at all with the truck so i know fuel pumps/relays etc are all good. fingers crossed, hopefully the rebuilt computer will fix that.
 
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