Rechipping the ECU

1093 Views 9 Replies 4 Participants Last post by DieLucas!, Mar 3, 2003

DieLucas!

Discussion Starter · Feb 21, 2003

haha...not a continuation of previous DiscoWeb rantings, but take a gander; maybe you can help me out...

Here's the deal, I bolted Slade's 14CUX EFI system (from manifold to ECU) on my 3.5. He had the ECU rechipped with a 4.2 chip for his 4.2 engine.

SO, effectively, I've got 4.2 fueling and air flow parameters running my 3.5. Problems? A few...

Mostly I have low-rpm hesistation. This usually occurs at steady-rpm driving and mild-acceleration...usually at low RPM. Keep in mind the engine idles fine and at freeway RPMs, everything is fine, too.
I've been getting a code for 40 and 50, which is ignition misfire on both banks. However, I doubt this is what is causing the hesitations/misfires...

Here's why:
if I increase the engine RPM (from the engine bay) and disconnect the mass-air meter, the engine will return to idle just fine AND the hesitation is completely gone!!!
Got that? The car drives better with the mass-air meter disconnected than when it's plugged in. I've never blown a mass-air code (only when I unplug it), and when I plug it back in the hesitation comes back.

So...I don't think I am having ignition problems, but I think 1) the mass air meter is heading south, or 2) I need to rechip the ECU with either a 3.9 chip or a 3.5 chip (this supposedly exists for late 80's/early 90's Discos in the UK using the 14CUX EFI) to move back within the parameter range intended for my engine's fueling and air-flow range.

Anybody have some insight? Personally, I think Mike knew this sh*t was jacked when I bought it which is why he was sooooooo surprised when I got it running :flipoff2: j/k Mikie!!!

I just bought a mass-air sensor off E-Bay for cheap and I've heard the 3.9 chips are a dime a dozen. Anybody got a scoop on a 3.9 or an elusive 3.5 chip laying around?

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lwg

· #2 · Feb 21, 2003

I can't really help you, but I do have a few questions.

What year truck are you running? I have a buddy with an '87 RRC and he is replacing the 3.5 with a 3.9 or a 4.2 if he can come up with the money. I figured he would have to use the 3.5 computer with the new engine. Will a 14CUX plug right into the factory harness on an '87 Rangie? This would be a good thing for him.

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DieLucas!

Discussion Starter · #3 · Feb 22, 2003

lwg said:
I can't really help you, but I do have a few questions.

What year truck are you running? I have a buddy with an '87 RRC and he is replacing the 3.5 with a 3.9 or a 4.2 if he can come up with the money. I figured he would have to use the 3.5 computer with the new engine. Will a 14CUX plug right into the factory harness on an '87 Rangie? This would be a good thing for him.

Mines an '83 and it was orignally carb'd.

I'm guessing your friend's '87 uses the Lucas 13CU EFI system. It should use a flapper-type air sensor as opposed to the hot-wire sensor and off the top of my head, I would imagine you would need a new harness.

Double check that, however. Give East Coast Rover a call and they will definitely be able to tell you whether you can just replace the ECU and the mass-air sensor or if you need the harness as well.

Sorry I can't give you more info. Try searching the internet, but you'll find the pickings are pretty slim.

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evilfij

· #4 · Feb 23, 2003

When you disconnect the MAF it goes into open loop. This is a common "get home" tactic. It could be any one of the sensors but disconnecting one eliminates them all (or at least most).

Ron

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DieLucas!

Discussion Starter · #5 · Feb 23, 2003

Because of the nature of the hesitation, it would likely be either the MAF or the TPS (or an ignition problem...). If the O2 sensors were suspect, I'd imagine they'd blow a code pretty quick. I've ran the engine open loop without the O2 sensors connected and I still get the hesitation.
If it were the TPS, the problem would still exist after pulling the MAF.

I talked with ECR since they often rechip along with their engine conversions. I can't remember who I talked to, but I found it humorous that they told me the Lucas ECU is pretty hard to fool, WRT whether my ignition fault codes were actually incorrect. That same day I pulled the MAF connection again and ran the car for nearly an hour before the code was displayed

Also on their recommendation, they told me to whack the MAF a couple of times with a hammer (I kid you not!!!). I did this and it appears to have fix the severity of the problem. Based on this and their info, the MAF is indeed the suspected component at this point. We'll see if the problem remains when the other MAF comes.

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DieLucas!

Discussion Starter · #6 · Mar 3, 2003

Not that anybody cares...but here's the update:

just got the mass-air sensor and it appears to have done the trick. No more hesitation. We'll see how long the driving stays good. I figure if push comes to shove, I'll try to convince the misses to put a new cam in the Disco (it's at 98K and needs a new front-cover seal...) and swap the 4.2 chip in my RR with the 3.9 in her Disco. Until then...

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UPOVR

· #7 · Mar 3, 2003

I thought all Range Rovers imported by RRNA were Lucas Hotwire? Mine is a 1988 and has lucas hotwire. I replaced my engine with 4.2 and used the original harness and plugged in a 4.2L 14cux computer, runs fine. The only thing I did change out was the fuel pressure regulator. Also mildly ported the heads and port matched intake and exhuast, crane cam and lifters. Smoked/locked up the spider gears in my front diff. It will white smoke my 235/85 MT's!

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DieLucas!

Discussion Starter · #8 · Mar 3, 2003 (Edited)

UPOVR said:
I thought all Range Rovers imported by RRNA were Lucas Hotwire? Mine is a 1988 and has lucas hotwire. I replaced my engine with 4.2 and used the original harness and plugged in a 4.2L 14cux computer, runs fine. The only thing I did change out was the fuel pressure regulator. Also mildly ported the heads and port matched intake and exhuast, crane cam and lifters. Smoked/locked up the spider gears in my front diff. It will white smoke my 235/85 MT's!

What's the question

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UPOVR

· #9 · Mar 3, 2003

no question just clarifying and supplying info!!

replying to your post that you said(die lucas) an 87 RR came with a flapper injection system. LWG was asking if his friend could swap in a 4.2L engine and run a 14cux computer. the answer to his question was yes if he has HotWire injection, which I am 95% sure he has.

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DieLucas!

Discussion Starter · #10 · Mar 3, 2003

Re: no question just clarifying and supplying info!!

UPOVR said:
replying to your post that you said(die lucas) an 87 RR came with a flapper injection system. LWG was asking if his friend could swap in a 4.2L engine and run a 14cux computer. the answer to his question was yes if he has HotWire injection, which I am 95% sure he has.

I don't know. I've seen references suggesting the hotwire system was introduced for the '88 MY; flapper systems were supposedly used on '87s, but maybe not NAS?

Anyway, visual inspection of the engine bay or ECU should tell you. If the air-meter looks like the flapper type (pics on www.rpiv8.com to help you differentiate), then you have the 4CU ECU which is basically a Bosch design. Everything must go! If you have a hot-wire mass air sensor, you likely have the 13CU ECU, and the harness appears to be interchangable with the 14CUX.

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