Piston Slap: May The Best Car Lose, Mr. Lutz: Mehta Challenges Cadillac's HT4100

Sajeev Mehta
by Sajeev Mehta

Yours truly, Sajeev Mehta writes:

Hello Piston Slappers, this S.O.S. is for anyone GM-savvy enough to tango with a 4.1L Cadillac. And live to diagnose another day: are you up for the challenge?

I acquired a 1986 Fleetwood 75 Formal Limousine (1 of 1000), which made me reconsider my stance on wrong-wheel drive GM products of the mid 1980s This was a $0.99 eBay purchase from a frustrated shipping company in the Houston Ship Channel who lost their overseas buyer. It didn’t run, until we installed a $20 ignition module. Which brought the less-than-a-buck Caddy back to life. Almost. So what’s the problem?

Tech Overload Warning! After fresh oil, coolant, belt, filters, vacuum lines, T-stat and a successful compression test, the trouble-prone HT4100 (at 84,000 miles) cannot idle below 1200 rpm, is hard to start, stalls going into gear and generates an E30 (ISC RPM Out Of Range) code. The ISC motor works and seems to be adjusted correctly. The TPS sensor is fine, according to the (ingenious) self-test on the dashboard. But these items needed replacement: coil, radiator, temperature sensor and alternator. While currently under $500 of capital invested, I’m now officially weary of throwing parts at this


So I am leaning toward addressing the Internet’s two biggest beefs with this Caddy: intake manifold gaskets (is there a horrendous vacuum leak?) or a worn distributor gear. There is some slack in the rotor, but those intake gaskets might be on their way out. Any guesses on resolving my problem? How offbeat is my latest diagnosis?

(Don’t waste bandwidth telling me to scrap the car: this Fleetwood has Farago-worthy levels of Cadillac brand equity in its copious hindquarters. Even the staffers at the 24 Hours of LeMons are in love. Chat with Autoblog’s Jonny Lieberman and Jalopnik’s Murilee Martin if you don’t believe me. More on that later.)

[Send your technical queries to mehta@ttac.com]

Sajeev Mehta
Sajeev Mehta

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  • Sajeev Mehta Sajeev Mehta on Oct 26, 2009

    +1 for the Doc. MadHungarian : No kidding! We saw the black Fleetwood's auction in February (I think) and the seller needed a full month to get a title to legally dump it on someone. I just consider ourselves lucky the Caddy didn't make a one way trip to Pick-A-Part when it got a proper TX title.

  • Jordan Tenenbaum Jordan Tenenbaum on Oct 27, 2009

    Always glad to see another HT4100 brought back to life. I once owned an `85 Brougham (RWD) equipped with the HT4100. I picked it up for free from someone who couldn't get it running. Turned out to be a rusted-through gas line. Fixed that, and then drove it around for awhile until the exhaust fell off and the transmission started doing its "start in the wrong gear" thing. I sold it to a guy for $400 and as far as I know he still has it. I would have repaired it and kept it, but it had a bunch of rust spots all over.

  • Bd2 Geeze, Anal sure likes to spread his drivelA huge problem was Fisher and his wife - who overspent when they were flush with cash and repeatedly did things ad hoc and didn't listen to their employees (who had more experience when it came to auto manufacturing, engineering, etc).
  • Tassos My Colleague Mike B bought one of these (the 300 SEL, same champagne color) new around June 1990. I thought he paid $50k originally but recently he told me it was $62k. At that time my Accord 1990 Coupe LX cost new, all included, $15k. So today the same car means $150k for the S class and $35k-40k for the Accord. So those %0 or 62k , these were NOT worthless, Idiot Joe Biden devalued dollars, so he paid AN ARM AND A LEG. And he babied the car, he really loved it, despite its very weak I6 engine with a mere 177 HP and 188 LBFT, and kept it forever. By the time he asked me to drive it (to take him to the dealer because his worthless POS Buick Rainier "SUV" needed expensive repairs (yes, it was a cheap Buick but he had to shell out thousands), the car needed a lot of suspension work, it drove like an awful clunker. He ended up donating it after 30 years or so. THIS POS is no different, and much older. Its CHEAPSKATE owner should ALSO donate it to charity instead of trying to make a few measly bucks off its CARCASS. Pathetic!
  • RHD The re-paint looks like it was done with a four-inch paintbrush. As far as VWs go, it's a rebadged Seat... which is still kind of a VW, made in Mexico from a Complete Knock-Down kit. 28 years in Mexico being driven like a flogged mule while wearing that ridiculous rear spoiler is a tough life, but it has actually survived... It's unique (to us), weird, funky (very funky), and certainly not worth over five grand plus the headaches of trying to get it across the border and registered at the local DMV.
  • Kat Laneaux I get the point that Musk is making. I wouldn't want everyone to know my secrets. If they did, they could or would shout it out to the world. But then, if Musk certified certain folks and had them sign Confidentiality agreements, which would allow them to work on cars that Musk had made, that could allow others to work on his cars and not confine vehicle owners to be charged an arm and a leg for the service. It's a catch 22. People are greedy little buggers. If they can find a way to make money, they will even if it wrong. People...sad.
  • 285exp I have been assured that EVs don’t require maintenance, so this seems pointless.